Review CH7

1. A snack food company produces bags of peanuts labeled as containing 3 ounces. Aconsumer reports organizatio¡¡lhinks this is incorrect, and wants to see if the weight isactuallylggg than 3 ounces. /fney randomly chooseSg-þags and their contents areweigheci. They find the aver@ weight is 2.85 ounces with a standard deviation of 0.5ounceslls this sufficient evidence to show that the bags contain less than 3 ounces ofpeanuÎõ? Use a significance level o15o/".

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test statistic value ol z=2.214. What is the corresponding pvalue? And is this significant atalpha=.05?

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3. ln 1965 , 44oh of the U.S. adult population had never smoked cigarettes. A national healthsurvey oll-?g5Jåndomly selected adults in 2011 revealed that9Jlhad never smokedcigarettes. Has there been a change in the proportion of U.S. adults that have never smokedcrgarenes? use a signrÍrcancffif 1ozo.

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4. Assuming that the population proportion is 44%, wha random sample of size 50?

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Review CHz

5. Sulfur compounds cause "off-odors" in.wine, so winemakers want the odorthreshold, the lowest concentration of a compound that the human can detect. The odor

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threshold for dimethyl sulfide (DMS) in trained wine tasters is aboutjS¡ticrograms per liter ofwine (¡rg/t). The untrained noses of consumers may be lggg sqlgj[e, however. Here are theOfr¡S óOor thresholds for 10 untrained students:

31, 31, 43, 36, 23, 34,32, 30, 20, 24

Are untraíned students less sensitive on the average than trained tasters in detecting "off-odors"in wine?

The units are micrograms of DMS per liter of wine (pg/l). Assume that the odor threshold foruntrained noses is"Normal¡v distr ls there evidence at the 1% level, that

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6. You read in a journal a report of a study that found a statistically significant result at the 5%significance leveÍ. What can you say about the significance of this result at the 1% teiel? Whichof the following is true. Circle your answer.

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It. may or may not be significant at the 1% level.

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Review Ch8

1. An article you read contains a g5% confidence interval. World the margin of error in a 99%confidence intervalcomputed form the same data be less, the same, or greater?

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2. A student organization plans to ask J-00¡andomly selected students how much they spent ontextbooks last semester. You argue for a sample ofpQQ students instead of 100. You know thatthe standard deviation of the sample mean of the amoin-'ts spent will be times as largewith the larger sample. What should the blank "____'l be?

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3. The makers of Brand X Cigarettes claim that the average nicotine content of their cigarettesis normal with a meqn that is gmg, with a standard deviation of l mg.

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We would now like tg use this cigarette data to construct ag}o/o confidence interval for the trueaverage amount of nicotine in a Brand X Cigarette

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Review Ch8

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5. Your measure_21_þxtbooks'weights, and find they have a meanAssu me the popul atio n stand ard devi atio n-j-s_9. 1 -çu¡ces.confidence interval for the toulÈopülãlion mean textbook weightm-LlT=C,qd=a,lZ¡'nt

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6. A student was asked to find a.9!)Zc-confidence intervalfor widget width using data from arandom sample of size n = 22. Which of the following is a correct interpretation of the interval14.2 < mu < 31.4? Check all the tare correct.

There is a 90% chance that the mean of the sample of 22 widgets will be wbyween 14.2and 31.4.

With 90% confidence, the mean width of a randomly selected widget will be between14.2 and31.4.

The mean width of all widgets is between 14.2 and 31.4, 90% of the time. We know thisis true because the mean of our sample is between 14.2 and 31.4.t/ With 90% confidence, the mean width of all widgets is between 14.2 and 31.4'11 There is a 90% chance that the mean of the population is between 14.2 and 31.4

7. For a confidence level of 90% with a sample size o-!QQ., find the criticqlt valueît^r-T ( ,oq)Li) =- 1,1 Ô33

8. Karen wants to advertise how many chocolate chips are in each Big Chip cookie at herbakery. She randomly selects a sample of.1ô4 cqokies and finds that the number of chocolatechops per cookie in the sample has a mean al 14.2 and a standard deviatio.¡_of 1.7. What is the90% confidence intervalfor the number ot cãõTa-rc chips per cookie tor ai'frtrõp-cookies?lnterpret the interval.(\ >LpL-td= tQ¡L3 =l'?40îo cT+-i'.lf

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Review Ch9

1. ln an experiment on the effect of brisk, prolonged walking on hemoglobin levels in blood, síxsubjects were used. The subjects were all similar with respect to mãny importantcharacteristics. ln the experiment, the hemoglobin level of each patient was measuredtwice:once before a long, brisk walk, and once immediately afterward. The data follows:

vratù*Q Pre-walk hemoglobin levelPost-walk hemoglobin level 1330 1140 1100 1460

1640 1370 1290 1480

there enough evidence to conclude that hemoglobin levels_decrease-on average during.prolonged, brisk walking? Conduct a test at the..lþ% lgvel of significance. lnclude all parts of thehypothesis test, and include what test you are usrng

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Review Ch9

2. Some researchers have investigated whether the air in carpeted rooms contains morebacteria than air in uncarpeted rooms. For an experiment, we have 5 rooms that are carpetedand 5 rooms that are uncarpeted. The rooms are similar in size. The concentration of bacteriain the air is measured in allof the rooms in number of bacteria per cubic foot. The data follows:

Carpeted Rooms: 236 244 170 220 250 flUft IUncarpeted Rooms: 180 160 178 18s 203 ,pú()L

ls there enough evidence to conclude at thq 3% level of significance that the air in carpetedrooms contains a-higlglgverage concentration of bacteria than that of the uncarpeted rooms.lnclude allthe paËãîÌiìã nypõtnesis test, including the test used, and conclusion.

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4. High levels of cholesterol in bloo are not healthy in mans or dogs. lt is plausiblethat dogs owned as pets have higher cholesterol levels than dogs owned by a veterinaryresearch clinic. "Normal" levels of cholesterol based on the clinic's dogs would then bemisleading. A clinic compared healthy dogs it owned with healthy pets brought to the clinic to beneutered. Here are the summary statistics for blood cholesterol levels in milligrams per deciliter:

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Pets 193174 Zsq".PT \Y!

C - \7 ,11 ) Çl ,112)A..j!Y" confidence interval for the difference in mean cholesterol levels between pets and clinicdogs is:

The following conclusion can be made:"We are 95% confident that mean cholesterol levels in pets is between the interval you

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3. A historian examining British colonial records for the Gold Coast in Africa suspects that thedeath rate was higher among African miners than among European miners. ln the year 1g36,there were.223 deaths among 33,809 African miners and 7 deaths among 1,541 Europeanminers in ú-e old Coast. - +-

Consider this year as a sample from the prewar era in Africa. ls there good evidence that theproportion of African miners who died during a year was_$gþglthan the proportion of Europeanminers who died? (State all parts of the hypotheses, inclúding the test used and the conclusion)

Review Gh9

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5. Suppose the Cartoon viewer attitudestoward Superman. Using a simple random sample, they select 400 boys and 300 girls toparticipate in the study. 160 boys say that Superman is their favorite character, compared to g0of the girls. Estimate the difference in attitudes towards Superman using a g5% confidenceinterval. State in works what their means in the context of this problem.

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