Ag engineering PE review: Ag engineering PE review: Exam prep, I-C economics and Exam prep, I-C economics and

statisticsstatistics

Marybeth Lima, Ph.D., P.E.Marybeth Lima, Ph.D., P.E.Cliff & Nancy Spanier Alumni Cliff & Nancy Spanier Alumni

ProfessorProfessorBiological & Agricultural Biological & Agricultural

EngineeringEngineeringE-mail: mlima1@lsu.eduE-mail: mlima1@lsu.edu

OverviewOverview Exam preparationExam preparation StatisticsStatistics Economic analysisEconomic analysis ThroughoutThroughout: :

You will be doing PE style problems You will be doing PE style problems (have your references and calculators (have your references and calculators ready!)ready!)

Ask questionsAsk questions

Part 1: Exam Part 1: Exam preparationpreparation

References (must have)References (must have) Time (in preparing for exam and Time (in preparing for exam and

during exam)during exam) Strategies (preparation and test Strategies (preparation and test

taking)taking)

ReferencesReferences Are an absolutely critical part of Are an absolutely critical part of

your preparation; you will not pass your preparation; you will not pass the exam without the proper the exam without the proper referencesreferences

There is a comprehensive list of There is a comprehensive list of references at references at http://www.asabe.org/membership/career-resourcespe-licensure/pei.aspx

Some references are more useful Some references are more useful than othersthan others

References I used for 80% References I used for 80% of the exam problems (must of the exam problems (must

haves)haves) A Guide to Professional Licensure for Agricultural, Food, A Guide to Professional Licensure for Agricultural, Food,

and Biological Systems Engineers (see online material)and Biological Systems Engineers (see online material) The notes from this on-line review course (bound)The notes from this on-line review course (bound) ASABE Standards (I used the 2000 edition for the 2005 ASABE Standards (I used the 2000 edition for the 2005

exam and was fine)exam and was fine) The Civil Engineering Reference Manual for the PE exam The Civil Engineering Reference Manual for the PE exam

(soil and water, wastewater, pumps, econ tables, INDEX)(soil and water, wastewater, pumps, econ tables, INDEX) The Mechanical Engineering Reference Manual for the The Mechanical Engineering Reference Manual for the

PE exam (HVAC, machine systems, econ tables, fans, PE exam (HVAC, machine systems, econ tables, fans, INDEX)INDEX)

You don’t have to bring both PE manuals but have one; I’d You don’t have to bring both PE manuals but have one; I’d recommend civil over mechanical because of broad coverage of recommend civil over mechanical because of broad coverage of topics. If you pick the civil manual, bring ASHRAE Fundamentals topics. If you pick the civil manual, bring ASHRAE Fundamentals or another strong HVAC book.or another strong HVAC book.

Other references I usedOther references I used Wastewater Engineering, Metcalf and Eddy Wastewater Engineering, Metcalf and Eddy

(used 3(used 3rdrd edition) edition) Henderson, Perry and Young, Principles of Henderson, Perry and Young, Principles of

Process EngineeringProcess Engineering Wood Engineering, Gurfinkel (any wood Wood Engineering, Gurfinkel (any wood

engineering book will do; you need the tables engineering book will do; you need the tables at the back; you may find in civil vs. ag parts at the back; you may find in civil vs. ag parts of library)of library)

A soil physics bookA soil physics book MWPS-1: Structures and Environment MWPS-1: Structures and Environment

Handbook (op)Handbook (op) Schwab et al. Soil and water conservation Schwab et al. Soil and water conservation

engineering (4engineering (4thth edition) edition)

References I brought and References I brought and did not usedid not use

Irrigation SystemsIrrigation Systems NRCS handbook parts 650 and 651NRCS handbook parts 650 and 651 Goering and Hansen, Engine and tractor Goering and Hansen, Engine and tractor

powerpower Shuler and Kargi, Bioprocess Shuler and Kargi, Bioprocess

Engineering Basic ConceptsEngineering Basic Concepts Salvendy, Handbook of Human FactorsSalvendy, Handbook of Human Factors MWPS-8, Swine Housing and Equipment MWPS-8, Swine Housing and Equipment

Handbook Handbook

Time: preparing for the Time: preparing for the examexam

Get your references and get used to using them (tab Get your references and get used to using them (tab Standards)Standards)

Make an index of where specific information is Make an index of where specific information is located so that you don’t have to search during the located so that you don’t have to search during the examexam

Do and re-do all the problems you are given in the on-Do and re-do all the problems you are given in the on-line courseline course

Do problems in your reference books (especially A Guide Do problems in your reference books (especially A Guide to Professional Licensure for ag, food and bio engineers)to Professional Licensure for ag, food and bio engineers)

Focus your time: general ag engineering knowledge, Focus your time: general ag engineering knowledge, your expertise area, your secondary knowledge areasyour expertise area, your secondary knowledge areas

Don’t spend time on what you KNOW you won’t touch Don’t spend time on what you KNOW you won’t touch (there is something you won’t)(there is something you won’t)

The week before the test, do a sample test using the 8 hr The week before the test, do a sample test using the 8 hr exam format (road test caffeine issues, etc.)exam format (road test caffeine issues, etc.)

Time during the examTime during the exam The exam is designed such that each question The exam is designed such that each question

takes an average of six minutestakes an average of six minutes There are 1 minute problems and 15-20 minute problemsThere are 1 minute problems and 15-20 minute problems

Go through the test and answer questions in the Go through the test and answer questions in the following order:following order: The quick, easy ones that you know you can doThe quick, easy ones that you know you can do The ones you know that you can do that take a little more The ones you know that you can do that take a little more

timetime Guess (with gusto!) at the ones that are beyond your scopeGuess (with gusto!) at the ones that are beyond your scope

Guess the same letter every timeGuess the same letter every time Go back and do the ones that you think you can do that are Go back and do the ones that you think you can do that are

time consumingtime consuming If there’s time, go back and check your answers; also go to If there’s time, go back and check your answers; also go to

the ones that are bugging you (if there are any)the ones that are bugging you (if there are any)

StrategiesStrategies You need to develop problem recognition You need to develop problem recognition You need to develop flexible thinkingYou need to develop flexible thinking Pick what you will not answer and guess with pleasure Pick what you will not answer and guess with pleasure

(I guessed at 10% of the questions on the exam)(I guessed at 10% of the questions on the exam) Many times you can eliminate two of the four choices Many times you can eliminate two of the four choices

easily (even with areas you know nothing about)easily (even with areas you know nothing about) The sample exam in the licensure book was very much The sample exam in the licensure book was very much

like the actual exam in terms of format and somewhat like the actual exam in terms of format and somewhat alike in terms of types of problems alike in terms of types of problems The exam doesn’t specify which section is which, but you’ll have four The exam doesn’t specify which section is which, but you’ll have four

or five consecutive questions that are from the same area and then or five consecutive questions that are from the same area and then on to the next area)on to the next area)

Knowing fundamental knowledge is critical (the PE Knowing fundamental knowledge is critical (the PE reference manuals in civil and mechanical were reference manuals in civil and mechanical were invaluable)invaluable)

StrategiesStrategies You need to answer ~60% of the problems You need to answer ~60% of the problems

correctly to passcorrectly to pass Having a strong base in general agricultural Having a strong base in general agricultural

engineering knowledge will “take you over the top”engineering knowledge will “take you over the top” My experience: for the various expertise areas, My experience: for the various expertise areas,

about 60% of the problems were solvable without about 60% of the problems were solvable without expert knowledge in the area (as long as you had expert knowledge in the area (as long as you had good references and knew where to look for info)good references and knew where to look for info)

The other 40% of the expertise questions were The other 40% of the expertise questions were expert knowledge level, involved problems (I expert knowledge level, involved problems (I skipped P&M, irrigation, and skipped P&M, irrigation, and structures/environment expert problems)structures/environment expert problems)

1-C: Economics and 1-C: Economics and statisticsstatistics

A broad area with applications “across the A broad area with applications “across the board” (5% of exam questions)board” (5% of exam questions) Statistics is commonly used because you need Statistics is commonly used because you need

descriptive information to help interpret datadescriptive information to help interpret data Economics is commonly used for making Economics is commonly used for making

engineering decisionsengineering decisions My suggestion for stats and econ: use the My suggestion for stats and econ: use the

CE or ME PE reference book (Lindeburg)CE or ME PE reference book (Lindeburg) Chapter on statistics Chapter on statistics

Table at the back (z-chart)Table at the back (z-chart) Get a t-chart as well!!Get a t-chart as well!!

Chapter on engineering economic analysisChapter on engineering economic analysis Full interest tables at the backFull interest tables at the back

Statistics basicsStatistics basics Measures of central tendencyMeasures of central tendency

Mean, median, modeMean, median, mode Measures of dispersionMeasures of dispersion

Standard deviation, variance, range, coefficient Standard deviation, variance, range, coefficient of varianceof variance

For PE: have equations to determine For PE: have equations to determine measures of central tendency and dispersionmeasures of central tendency and dispersion

There are slight differences in equations There are slight differences in equations depending on if you are working with a depending on if you are working with a population or a samplepopulation or a sample

Statistics: DistributionsStatistics: Distributions A number of distributions can be used A number of distributions can be used

to describe various data sets or can be to describe various data sets or can be used to solve engineering problems in used to solve engineering problems in relation to these data setsrelation to these data sets Sampling distributions involving means:Sampling distributions involving means:

Normal (aka Gaussian): our focusNormal (aka Gaussian): our focus Student t distributionStudent t distribution

Sampling distributions involving variance:Sampling distributions involving variance: F distributionF distribution Chi-SquareChi-Square

Normal distribution: Normal distribution: reviewreview

Symmetrical distribution with Symmetrical distribution with mean mean and standard deviation and standard deviation

Area under curve represents Area under curve represents 100% of possibilities100% of possibilities 50% to the right of the mean50% to the right of the mean 50% to the left of the mean50% to the left of the mean

A value is higher than the mean A value is higher than the mean for this distribution to the right for this distribution to the right of the mean, lower to the left of of the mean, lower to the left of the meanthe mean

x represents where you are in x represents where you are in the distribution; z is the number the distribution; z is the number of standard deviations away of standard deviations away from the mean that you arefrom the mean that you are z is positive to right of meanz is positive to right of mean z is negative to left of meanz is negative to left of mean

xz

xz

xz

xz

Reading the z-chartReading the z-chart

Typical PE style Typical PE style problemsproblems

The population mean for college The population mean for college students’ heights is 67 inches, and students’ heights is 67 inches, and the population standard deviation is the population standard deviation is and 4 inches. These data are and 4 inches. These data are normally distributed.normally distributed. What percentage of college students What percentage of college students

have heights less than 71 inches? have heights less than 71 inches?

)18.259.0( zP

SolutionSolution

In what range would you find the In what range would you find the middle 70% of the data? (pick closest z middle 70% of the data? (pick closest z value, do not interpolate)value, do not interpolate)

SolutionSolution

You try this one:You try this one: 90% of college students have heights 90% of college students have heights

greater than what value?greater than what value?

SolutionSolution

SamplingSampling We almost never work with populationsWe almost never work with populations We take samples and try to draw We take samples and try to draw

conclusions about a population based conclusions about a population based on a sampleon a sample Use z chart for large samples (n>30)Use z chart for large samples (n>30) Use t chart for small samplesUse t chart for small samples

Your statistical equations change a Your statistical equations change a little to reflect the fact that you have a little to reflect the fact that you have a samplesample

nxz

xz

Confidence intervalsConfidence intervals Commonly used in research and Commonly used in research and

process controlprocess control 95% confidence intervals are common95% confidence intervals are common For example, what is the 95% For example, what is the 95%

confidence interval of a set of 50 data confidence interval of a set of 50 data points; the mean of this data set is points; the mean of this data set is 150 and the standard deviation is 15.150 and the standard deviation is 15.

z nz

2

nstx

2

SolutionSolution

Hypothesis testingHypothesis testing Used to compare means values to each other to Used to compare means values to each other to

determine if they’re significantly differentdetermine if they’re significantly different ConsiderationsConsiderations

What kind of hypothesis test is it?What kind of hypothesis test is it? Sample mean (large or small) compared to a standardSample mean (large or small) compared to a standard Sample mean (large or small) compared to another sample Sample mean (large or small) compared to another sample

mean (large or small)mean (large or small) Will you use a t chart or a z chart?Will you use a t chart or a z chart?

Is the test one tailed (where directionality matters) Is the test one tailed (where directionality matters) or two tailed (when only difference between values or two tailed (when only difference between values matters)matters)

nsxt

Steps to hypothesis Steps to hypothesis testingtesting

Ask, “what am I trying to show?” Ask, “what am I trying to show?” this is the alternate hypothesisthis is the alternate hypothesis The null hypothesis contains all the other The null hypothesis contains all the other

possibilitiespossibilities Construct the acceptance and rejection Construct the acceptance and rejection

region for the hypothesis region for the hypothesis Calculate the test statisticCalculate the test statistic Determine whether to accept or reject the Determine whether to accept or reject the

null hypothesis (you always test the null)null hypothesis (you always test the null)

Reading a t chartReading a t chart

Example, hypothesis Example, hypothesis testingtesting

A biodiesel plant has a standard daily A biodiesel plant has a standard daily production rate that is normally production rate that is normally distributed with a mean of 880 distributed with a mean of 880 tons/day. Sampling the plant once a day tons/day. Sampling the plant once a day for 35 days yielded a mean output of for 35 days yielded a mean output of 870 tons/day with a standard deviation 870 tons/day with a standard deviation of 20 tons per day. Do the data present of 20 tons per day. Do the data present sufficient evidence to show that the sufficient evidence to show that the output is less than the standard?output is less than the standard?

1. Construct alternate and 1. Construct alternate and null hypothesesnull hypotheses

Problem statement: show output is Problem statement: show output is less than standardless than standard Ha: Ha: < 880 < 880 Null is every other possibility: Ho: Null is every other possibility: Ho: ≥ ≥

880880 From this statement, we can see that From this statement, we can see that

directionality (< or >) matters: one-tailed testdirectionality (< or >) matters: one-tailed test If directionality doesn’t matter (show that the If directionality doesn’t matter (show that the

means are different): two-tailed testmeans are different): two-tailed test

2. Construct 2. Construct acceptance/rejection regionacceptance/rejection region Start by drawing the standard that Start by drawing the standard that

your sample is being compared toyour sample is being compared to You need to know four things:You need to know four things:

Which side of the mean your sample Which side of the mean your sample mean falls on (to right/left of mean)mean falls on (to right/left of mean)

What is alpha? (standard = 0.05)What is alpha? (standard = 0.05) One-tailed or two tailed testOne-tailed or two tailed test Will you use the t-chart or z-chart?Will you use the t-chart or z-chart?

The four things:The four things: Sample mean is 870, which is less Sample mean is 870, which is less

than 880, so you’re to the left of the than 880, so you’re to the left of the meanmean

Alpha is not given, assume 0.05Alpha is not given, assume 0.05 Directionality matters, (<), one-Directionality matters, (<), one-

tailedtailed n = 35, >30, use the z chartn = 35, >30, use the z chart

Acceptance/rejection Acceptance/rejection regionregion

Calculate the test Calculate the test statisticstatistic

Draw the conclusion: Draw the conclusion: accept or reject the null accept or reject the null

hypothesishypothesis z-crit = -1.645z-crit = -1.645 z-calc = -2.95z-calc = -2.95 If you draw z-calc on your If you draw z-calc on your

acceptance/rejection region, it falls into acceptance/rejection region, it falls into the portion of the curve in which the null is the portion of the curve in which the null is rejectedrejected

Thus, reject the null and conclude that Ha Thus, reject the null and conclude that Ha is true: yes, sufficient evidence exists for is true: yes, sufficient evidence exists for showing that the mean output of the plant showing that the mean output of the plant is less than 880is less than 880

DrawingDrawing

Statistics summaryStatistics summary General Tips: General Tips:

Get a general reference with equations Get a general reference with equations and make sure you have a z chart and a and make sure you have a z chart and a t chartt chart get z from A, and A from zget z from A, and A from z Know confidence intervalsKnow confidence intervals Look at process control (2 and 3 sigma Look at process control (2 and 3 sigma

limits)limits)

Statistics summary, Statistics summary, hypothesis testinghypothesis testing

Very cookbook approachVery cookbook approach When you draw the acceptance/rejection When you draw the acceptance/rejection

region, draw the mean that you are region, draw the mean that you are comparing your sample to firstcomparing your sample to first When comparing two small samples, When comparing two small samples,

arbitrarily choose one and make sure you arbitrarily choose one and make sure you keep the means properly situated from a keep the means properly situated from a numerical standpointnumerical standpoint

Also remember that sample size is POOLED or Also remember that sample size is POOLED or added, so df = n1 + n2 - 2added, so df = n1 + n2 - 2

Remember that you always test the null Remember that you always test the null hypothesis, which leads to a conclusion about hypothesis, which leads to a conclusion about the alternatethe alternate

1-C: Engineering 1-C: Engineering economic analysiseconomic analysis

Typically easy questions on the exam if you know Typically easy questions on the exam if you know how to use factor tables (slang, interest tables)how to use factor tables (slang, interest tables) Tabulated in the ME reference manual, A-132-150 or CE Tabulated in the ME reference manual, A-132-150 or CE

manual A-112-130manual A-112-130 Types of problems in engineering economic analysisTypes of problems in engineering economic analysis

Decision making: you have a material you’re trying to Decision making: you have a material you’re trying to choose, or a part, or a machine. Compare which is most choose, or a part, or a machine. Compare which is most economical given present cost, maintenance costs, etc.economical given present cost, maintenance costs, etc.

Replacement/retirement analysis (when should you replace Replacement/retirement analysis (when should you replace or retire a product?)or retire a product?)

Rate of return problem (to find percentage return on an Rate of return problem (to find percentage return on an investment)investment)

Break even point on an investment Break even point on an investment Loan repayment (how long will it take)Loan repayment (how long will it take) Economic life analysis (life cycle costs)Economic life analysis (life cycle costs) Benefit/cost analysis (do the benefits outweigh the costs)Benefit/cost analysis (do the benefits outweigh the costs)

Engineering econEngineering econ Almost all engineering econ problems will involve Almost all engineering econ problems will involve

cashcash flowsflows; it is like a material balance using money ; it is like a material balance using money instead of mass.instead of mass.

Types of cash flows:Types of cash flows: Single payment cash flows (P or F)Single payment cash flows (P or F)

P = present value of moneyP = present value of money F = future value of moneyF = future value of money

Uniform series cash flow (A) Uniform series cash flow (A) An amount that is the same every month, like a house or car An amount that is the same every month, like a house or car

paymentpayment Gradient series cash flow (not used much) (G)Gradient series cash flow (not used much) (G)

A value that goes up or down the same amount every time periodA value that goes up or down the same amount every time period You use types of cash flows to compare alternatives You use types of cash flows to compare alternatives

and solve econ problemsand solve econ problems

Engineering econEngineering econ Cash flow Cash flow

problems can be problems can be calculated using calculated using equations or are equations or are tabulated for fast tabulated for fast problem solvingproblem solving

ExampleExample If you put $1,000 into a savings account If you put $1,000 into a savings account

and the annual interest rate on the and the annual interest rate on the account was 6%, how much money account was 6%, how much money would be in the account after 5 years?would be in the account after 5 years?

The equation to convert a present The equation to convert a present value to a future value is value to a future value is

niPF )1(

Engineering econEngineering econ (1 + i)(1 + i)nn is called the single payment compound is called the single payment compound

amount factor, and is tabulated for various amount factor, and is tabulated for various combinations of i (interest rate) and n (time combinations of i (interest rate) and n (time period)period)

The notation (symbol) for the single payment The notation (symbol) for the single payment compound factor is (F/P, i%, n)compound factor is (F/P, i%, n)

This notation indicates that F (future $ This notation indicates that F (future $ amount) is unknown, that you have P (the amount) is unknown, that you have P (the present value), and given the interest rate (i) present value), and given the interest rate (i) in percent and the time period (n), you can in percent and the time period (n), you can find F.find F.

Engineering econEngineering econ Back to our example: If you put Back to our example: If you put

$1000 into a savings account and the $1000 into a savings account and the annual interest rate on the account annual interest rate on the account was 6%, how much money would be was 6%, how much money would be in the account after 5 years?in the account after 5 years?

Solve by equation: F = 1000(1 + Solve by equation: F = 1000(1 + 0.06)0.06)5 5 = $1338.23= $1338.23

Solve by interest tableSolve by interest table

Engineering econEngineering econ

Engineering econEngineering econ Example solve by interest table:Example solve by interest table:

Go to F/P column with n = 5, for table Go to F/P column with n = 5, for table with i = 6%: Factor = 1.3382with i = 6%: Factor = 1.3382

F = ($1000) 1.3382 = $1338.2F = ($1000) 1.3382 = $1338.2

n) i%, (F/P,PF

n) i%, (F/P,PF

Engineering econEngineering econ Biggest thing to keep in mind: make Biggest thing to keep in mind: make

sure that your UNITS match; interest sure that your UNITS match; interest rate, n, and dollar amounts may be rate, n, and dollar amounts may be given on a different basisgiven on a different basis

You try: How much should you put You try: How much should you put into a 10% effective annual rate into a 10% effective annual rate savings account in order to have savings account in order to have $10,000 in four years? (10% interest $10,000 in four years? (10% interest table included on next page)table included on next page)

Engineering econEngineering econ

Engineering econEngineering econ You are given a future amount of money (F) You are given a future amount of money (F)

and ask to solve for a present amount of and ask to solve for a present amount of moneymoney

Solve using the i = 10% interest table, with Solve using the i = 10% interest table, with n = 4 years; (P/F, 10%, 4) = 0.6830n = 4 years; (P/F, 10%, 4) = 0.6830

P = F (P/F, 10%, 4) = $10,000*0.6830 = P = F (P/F, 10%, 4) = $10,000*0.6830 = $6,830$6,830

Notice that n is given in years and i is given Notice that n is given in years and i is given as an annual interest rate (per year); units as an annual interest rate (per year); units matchmatch

Engineering econEngineering econ Maintenance costs for a machine are Maintenance costs for a machine are

$250/year. What is the present $250/year. What is the present worth of these maintenance costs worth of these maintenance costs over a 12 year period if the annual over a 12 year period if the annual interest rate is 10%?interest rate is 10%? Given:Given: Find:Find:

Engineering econEngineering econ You have A, you need P: Go to i = You have A, you need P: Go to i =

10% interest chart and go to the P/A 10% interest chart and go to the P/A column (remember in this notation column (remember in this notation your unknown comes first): (P/A, your unknown comes first): (P/A, 10%, 12) = 6.813710%, 12) = 6.8137

P = A (P/A) = -250*6.8137 = -$1703 P = A (P/A) = -250*6.8137 = -$1703 (negative sign indicates a cash sink (negative sign indicates a cash sink or loss of $)or loss of $)

More complicatedMore complicated Question 104, webinar questions on general Ag Eng Question 104, webinar questions on general Ag Eng

principlesprinciples As manager of a large fleet of farm equipment, you are

contracting with an outside mechanics shop to have all complete engine overhauls for tractors, combines, and harvesters at the rate of $7,200 per engine. You have determined the investment needed to construct a new building and equip it to overhaul the equipment yourself would be $180,000. The estimated annual cost for taxes and insurance for the facilities and equipment is 1.25% of the purchase price. The operating cost to perform engine overhauls at a facility that you own would be $5,500 per engine. The equipment and facilities are assumed to have a life of 12 years with a salvage value of $35,000. Interest rate is 7% per year. The minimum number of engines to be overhauled per year to make the investment in equipment and facilities economically feasible is:

NOTE: use 7% interest table (extra handout)NOTE: use 7% interest table (extra handout)

SolutionSolution Approach:Approach:

You are comparing two alternatives, outsourcing You are comparing two alternatives, outsourcing vs. doing it yourselfvs. doing it yourself

Outsourcing: $7200 per engineOutsourcing: $7200 per engine ““in-sourcing”: $5500 per engine, plus facilities, in-sourcing”: $5500 per engine, plus facilities,

equipment, taxes, and insurance (and minus salvage equipment, taxes, and insurance (and minus salvage value)value)

You have to compare these two alternatives using You have to compare these two alternatives using the same basisthe same basis

Choose AChoose A Identify which type of cash flow you have in each situationIdentify which type of cash flow you have in each situation Set the outsourcing term = in-sourcing termSet the outsourcing term = in-sourcing term Solve for x, where x is the number of engines needed to Solve for x, where x is the number of engines needed to

break evenbreak even

SolutionSolution Outsourcing: $7200/engine * x engines, or Outsourcing: $7200/engine * x engines, or

$7200x$7200x ““In-sourcing:”In-sourcing:”

$5500/engine * x engines, or $5500x$5500/engine * x engines, or $5500x New building and equipment = $180,000 (P)New building and equipment = $180,000 (P)

Convert to AConvert to A Interest = 1.25% of building/equipment per year (A)Interest = 1.25% of building/equipment per year (A)

0.0125*180,000 = $22500.0125*180,000 = $2250 Salvage value = $35,000 12 years from now (F)Salvage value = $35,000 12 years from now (F)

Convert to AConvert to A Use equations (as in solution online) OR Use equations (as in solution online) OR

(EASIER): use interest tables!(EASIER): use interest tables!

SolutionSolution

SolutionSolution

Engineering economics Engineering economics summarysummary

Also very cookbook approach, like Also very cookbook approach, like statisticsstatistics

Identify which factors you’re working Identify which factors you’re working with (F, A, P, G) and ensure that you with (F, A, P, G) and ensure that you use the same basis (usually annual)use the same basis (usually annual)

Interest tables speed the solving of Interest tables speed the solving of these problems; obtain a set of these problems; obtain a set of interest tables!interest tables!

Take home pointsTake home points If your brain feels like it’s leaking out If your brain feels like it’s leaking out

of your ears right now, don’t worry, it’s of your ears right now, don’t worry, it’s normal normal

Best things I did for the PE: Best things I did for the PE: Had a reference book with a great indexHad a reference book with a great index Had a list of where to find critical Had a list of where to find critical

equations and important informationequations and important information Time management tips Time management tips GOOD LUCK!!GOOD LUCK!!

Exam prep exercisesExam prep exercises

““Use of your PE reference books” Use of your PE reference books” exerciseexercise

On the PE exam, you want the “1 minute questions” On the PE exam, you want the “1 minute questions” that appear on the test to take 1 minute to answerthat appear on the test to take 1 minute to answer

These questions are testing your basic knowledge of These questions are testing your basic knowledge of the field and your ability to bring and use the proper the field and your ability to bring and use the proper referencesreferences

Practice: find the answers to the questions on the Practice: find the answers to the questions on the following slides following slides ApproachApproach

First, classify the problem: in which area of the Ag PE do you First, classify the problem: in which area of the Ag PE do you think the problem is contained? In which references might you think the problem is contained? In which references might you find the information?find the information?

When you find the answer, record the value, the reference in When you find the answer, record the value, the reference in which you found the answer, AND descriptive information which you found the answer, AND descriptive information within the reference (page number, table number, figure within the reference (page number, table number, figure number, equation number, etc.)number, equation number, etc.)

Question 1Question 1 What is the heat of combustion of What is the heat of combustion of

propane?propane?

NOTE: heat of combustion is also NOTE: heat of combustion is also referred to as heating valuereferred to as heating value

Heat of combustionHeat of combustion

Question 2Question 2 The Atterburg limit test measures The Atterburg limit test measures

what?what?

Question 3Question 3 What is the Young’s modulus of What is the Young’s modulus of

elasticity of stainless steel?elasticity of stainless steel?

Question 4Question 4 What is the density of air at 10° C?What is the density of air at 10° C?

Question 5Question 5 What is the curve number for What is the curve number for

contoured row crops in good contoured row crops in good hydrologic condition for hydrologic hydrologic condition for hydrologic soil group B?soil group B?

Question 6Question 6 For a relatively uniform distribution For a relatively uniform distribution

of soil particles 1 mm in diameter, of soil particles 1 mm in diameter, what is the largest sieve size that what is the largest sieve size that these particles would not pass these particles would not pass through?through?

Question 7Question 7 What is the typical concentration of What is the typical concentration of

suspended solids (SS) in septage?suspended solids (SS) in septage?

Question 8Question 8 What is the equilibrium moisture What is the equilibrium moisture

content of rough rice at 30° C and content of rough rice at 30° C and 80% RH?80% RH?

Question 8Question 8

Questions on this Questions on this exercise?exercise?

In my experience, 10-20% of the In my experience, 10-20% of the questions on the exam were of this questions on the exam were of this naturenature Fast if you had the right references and Fast if you had the right references and

knew where to find the informationknew where to find the information

Hypothesis testing Hypothesis testing problemsproblems

Suppose you take dissolved oxygen Suppose you take dissolved oxygen (DO) samples in a stream; the mean (DO) samples in a stream; the mean DO is 4.9 mg/l and the standard DO is 4.9 mg/l and the standard deviation is 0.3 mg/l. Your data sample deviation is 0.3 mg/l. Your data sample consists of 8 samples. The minimal DO consists of 8 samples. The minimal DO level necessary in the stream is 5.0 level necessary in the stream is 5.0 mg/l. Does your sample data meet this mg/l. Does your sample data meet this minimal standard? Use standard minimal standard? Use standard hypothesis testing conditions.hypothesis testing conditions.

Hypothesis testing Hypothesis testing questionquestion

You took a second set of samples (same You took a second set of samples (same location) at the same stream a month location) at the same stream a month later. This time, your data show a mean later. This time, your data show a mean DO level of 5.2 mg/l with a standard DO level of 5.2 mg/l with a standard deviation of 0.5 mg/l. This data set also deviation of 0.5 mg/l. This data set also has 8 samples. Complete a hypothesis has 8 samples. Complete a hypothesis test to show if the DO levels in the stream test to show if the DO levels in the stream are different (between last month and are different (between last month and this month). Use standard hypothesis this month). Use standard hypothesis testing conditions.testing conditions.