Design an Experiment

Like a Real Scientist!!

This is timely

Let’s review what science is

• This should do it. 8 min.

• And that elusive definition of a THEORY

• http://www.youtube.com/watch?v=9Re8QxKZdm0 7:30

• And a LAW is what?

Identify and describe questions that can be answered through science and which questions are outside the boundaries of science.

Follow precisely a complex

multistep procedure when

carrying out experiments, taking

measurements, or performing

technical tasks.

Translate quantitative technical

information expressed in words

in a text into visual form (table,

graph).

Use tools to gather, analyze, and

interpret data.

Pose answers, explanations, or

descriptions of events and

natural phenomena.

Identify sources of information

and assess their reliability

according to the strict standards

of scientific investigation.

Explain why a scientific theory

cannot become a law and why a

law cannot become a theory.

Describe the steps of

the scientific method.

Generate a hypothesis.

Use tools to gather

data.

Identify what is science

and what is not science.

List the steps of the scientific method.

Define: Science

Observation

Theory

Law

Hypothesis

Inference

Bias

Pseudoscience

Peer review

Qualitative data

Quantitative data

Independent

variable

Dependent variable

Constant variable

Control

Identify tools used to gather data.

Research question

• Science always starts with an observation that leads to some questions.

• Start with the general topic, then narrow it down to a more specific question. Often you will start with an observation.

• Example: I’ve seen people use fertilizer. Fertilizing is a common way to enhance plant growth. What effect will the four best selling fertilizers have on the growth of the common lima bean plant?

• Do a little research.

Hypothesis

• Be specific.

• It must be testable.

• Example: If the number of different nutrients in a fertilizer affects plant growth, then Mighty Grow will cause the most growth because it has a greater number of nutrients than the other three leading brands.

Formalized Hypotheses example: If people have a high exposure to uv light, then they will have a higher frequency of skin cancer because uv light can cause mutations.

Notice that these statements contain the words , ifand then and because. They are not necessary in a formalized hypothesis, but it helps make it consistent for you. But not all if-then statements are hypotheses. For example, "If I play the lottery, then I will get rich." This is a simple prediction. In a formalized hypothesis, a tentative relationship is stated. For example, if the frequency of winning is related to frequency of buying lottery tickets. "Then" is followed by a prediction of what will happen if you increase or decrease the frequency of buying lottery tickets. Then the reason follows the word “because”.

Choose your subjects

• This is often a matter of availability and cost, unless you had a specific subject in mind from the start.

Choose your equipment

• This will often depend on availability and cost.

• Separate pots for each plant? Soil type? Water source? Light?

Dependent Variable?

• What will you measure? How, exactly?

• Height? From where to where? With what instrument?

• Mass? How will you remove dirt from roots? Instrument? Can you measure this on a daily basis?

• Decide what is best.

Speaking of Measuring…

• Be very careful and PRECISE when you measure.

• If your measuring tool is not digital, you are allowed and EXPECTED to judge to one digit past the smallest marks on the device.

• For example, if your meter stick is marked off (graduated) in millimeters, don’t round to centimeters. Carefully judge to tenths of a millimeter.

Variable control

• Think of ALL the variables that may affect your dependent one. Research is necessary here, as well as common sense.

• Now plan for exactly HOW you will control all these.

• “Control” means to keep them the same for all subjects, right?

• Let’s practice.

Control group?

• This is a different concept than controlling variables, but is related. The control group will help control variables, but it’s main purpose is to give you something to compare your experimental group(s) to.

• How do you know your independent variable has ANY effect?

• In this case, growing a set of plants with no fertilizer would do the trick.

• Sometimes there won’t be a control group. Boys vs. girls heartrates, for example.

Practice? You talking about practice?

• Have you accounted for a practice effect?

• How about a fatigue effect?

• If you have groups, are they about the same?

Repetition

• In order for your results to reliably and validly show the affect of the independent variable, you want to test it repeatedly.

• This can be done either with repeated measurements of the same subject, or with many subjects.

• In our case, since all bean plants are a bit different, grow many plants to even out these differences.

• At least 10 subjects in each group is a good idea.

As you Plan…

• Keep remembering your hypothesis. Don’t start adding other factors like different plants or light amount.

Blind? Double blind?

• If it applies, the subjects should not know what treatment they are getting as it might affect their response to it.

• The classic example is with medicine. If you have a group getting a medicine and a control group getting a placebo (like a pill that has no medicine in it), the subjects should not know which they are getting (they should be blind).

• Double blind would be when the giver of the medicine doesn’t know which one it is.

How to record data?

• Construct a table.

• Consult The Use of Tables and Figures.

How to analyze data?

• Compare using statistics.

• T-test? Chi square?

• Remember, you are trying to take judgment and subjectivity out of the picture.

Constantly observe!!

• Observe if what you are doing is what you intended to do.

• If anything happens that you think might affect the experiment, make detailed notes of it as you experiment so that you can consider how you will account for it when all is said and done. Use a lab notebook for this.

• For example, what if the lights go out for one of your plant groups?

Then what, to make this SCIENCE?

• Then your write-up is sent to a journal for a critical step – peer review.

• A group of experts (peers) will dissect your paper and see if it holds up to intense scrutiny.

• Did you control all variables?

• Did you do the analysis (math) correctly?

• Did you come to a valid conclusion based on the results?

• Then – the Nobel Prize, and you are famous!

So let’s watch this and review

• http://www.youtube.com/watch?v=zcavPAFiG14 10 min.

• How might you use SCIENCE to figure out something like – what pitch is best to use on an 0 and 2 count?

Biology Quarter 1

EOC tested standards review

SC.912.N.1.1

SC.912.N.1.1Benchmark clarifications

• Students will:• Design/evaluate a scientific investigation using evidence of scientific

thinking/problem solving

• Analyze/interpret data to make predictions and/or defend conclusions

• Compare/contrast structure & function of various microscopes

• Evaluate merits of scientific explanations produced by others

• Assess reliability of sources of information according to scientific standards

• Describe how scientific inferences are made from observation AND identify examples from biology

1. Danielle conducted an experiment to determine if listening to different styles of music would affect a person’s pulse. Her hypothesis was that pulse rate would change with different types of music. Each person in the experiment listened to seven different selections of music, for thirty seconds each. Each person’s pulse was taken before the music & than after each 30-second interval of music. The pulses were taken again after the music selections were completed. Based on her experiment, Danielle concluded that a person’s pulse rate changed when the person listened to different types of music. Which component is missing from Danielle’s experiment?A. a questionB. a manipulated variableC. a control groupD. a description of the experiment

2. Many plants and trees, with the help of a nitrogen-fixing bacteria, take nitrogen from the air and convert it into a usable form. A student wants to find out if the redbud tree helps to put nitrogen into the soil. She designs an experiment in which she measures the amount of nitrogen in the soil around redbud trees and pine trees, before and after nitrogen-fixing bacteria are added to the soil. What is a logical hypothesis for the student’s experiment?A. Nitrogen-fixing bacteria increase soil nitrogen levels.B. Redbud trees grow faster when soil nitrogen is present. C. Redbud trees increase soil nitrogen levels with the help of nitrogen-

fixing bacteria.D. Nitrogen-fixing bacteria populations grow faster when soil nitrogen is

present.

Now, go back and analyze the student’s plan. What are possible flaws in the design of the experiment?

How should the student label the axes of a graph to illustrate the data from the nitrogen-fixing experiment?

Review the original Redbud scenario and answer these questions:

What is the dependent variable in the experiment?A. Tree typeB. Type of bacteriaC. Amount of soil measuredD. Amount of soil nitrogen measured

Which of these is a biotic factor in the environment of a redbud tree?

A. Air temperatureB. The number of beesC. The amount of sunlightD. The amount of nitrogen in the air

3. A researcher designed an investigation to test what effect eating different types of food would have on blood insulin levels. She selected 10 male subjects who were all 25 years of age and in good health. The experiment took place over 3 days. At 8:00AM on each day, the subjects ate a meal consisting of only 1 type of food. They had their blood insulin levels measured after consuming the meal. ON Day 1 they ate a diet high in fat, on day 2 they ate a high protein diet, and on Day 3, that ate a high sugar diet.

What is the independent variable in this experiment?A. The age of the subjectsB. The blood insulin levelC. The type of food consumedD. The time of day the meal was consumed

4. Caroline is designing an experiment to test the hypothesis that exposure to an increased level of ultraviolet radiation reduces the growth of corn plants. She has 200 corn seedlings planted in two groups of 100 seedlings each. She is trying to decide how much water, fertilizer, and ultraviolet radiation each group should receive. Which of the factors should she keep the same in both plant groups in order to successfully test the hypothesis? A. Amount of fertilizer onlyB. Amount of fertilizer and waterC. The amount of ultraviolet radiation onlyD. The amount of fertilizer, water, and ultraviolet

radiation

5. Ants and beetles compete for resources in some elevations. Scientists collected leaf litter from different elevations. The scientists recorded the number of ants & the number of beetles found in the leaf litter at each elevation and created graphs showing the data. Which conclusion do the data BEST support?

A. Ants are the prey species of beetlesB. Ants have high survival rates with fewer competitors.C. Ants have large populations when many beetles are in the communityD. Ants are more likely to survive at higher elevations that at lower elevations.

6. Cells known as “chemoreceptors” respond to changes in the carbon dioxide level of the blood. When these chemoreceptors are stimulated, they send impulses that increase breathing. The increased breathing lowers the blood’s carbon dioxide level. The body typically functions best when the level of carbon dioxide is 40 mm Hg. When the chemoreceptors encounter carbon dioxide levels higher than this, they increase their activity. Which of these graphs best shows the relationship between level of carbon dioxide and chemoreceptor activity?

7. A horticulturist hypothesized that if he increases the level of carbon dioxide (CO2) in the air of his greenhouses, then his plants will absorb

carbon more quickly. He collected the following data from an experiment performed on his plants.

Which statement is true about the data in the table?A. The data supports the hypothesis because the plants grew more when the level of CO2

increased.B. The data supports the hypothesis because the plants grew less when the level of CO2

increased.C. The data contradicts the hypothesis because plants grew less when the level of CO2 increased.D. The data contradicts the hypothesis because the plants grew more when the level of CO2

increased.

8. The diagram below shows a setup for plant investigation. Which variable is most likely being tested?

A. Hours of light exposure

B. Plant species

C. Soil volume

D. Soil pH

9. The graphs (below) show the results of 2 separate experiments on the same species of plant. Students now want to determine how the use of rainwater or bottlede water affects the

growth of this plant. Which conditions should be used for optimal growth as the 2 water types are tested?

A. 20°C, 10 mL/day

B. 25°C, 35 mL/day

C. 30°C, 45 mL/day

D. 35°C, 20 mL/day

10. These three samples from the same live bacterial culture were all viewed at the same magnification. Which conclusion is best

supported by observation of these three samples?

A. The bacterial culture was unaffected by

the chemical agent.

B. The sampling techniques used did not

produce accurate data.

C. The culture became contaminated by

airborne bacteria during the initial

sampling

D. The culture included some bacteria that

were resistant to the chemical agent.

11. Many residents in a small town have developed a bacterial infection. Two students hypothesize that the bacteria are coming from the town’s drinking water. They look for the bacteria in water samples from the lake that supplies about 80% of the town’s drinking water. When they find no bacteria, the students conclude that the town’s residents are not getting the bacteria from their drinking water. Which is a source of error in the students’ experimental design?

A. Water from the lake was not tested for other possible pathogens.

B. Residents of other nearby towns were not tested for the bacteria.

C. The residents’ genetic predisposition for getting ill was not determined.

D. Other sources of drinking water were not tested for bacteria.

12. A student plans to conduct an experiment to determine how a change in the pH of water affects the population growth rate of algae. To ensure that her experimental data are valid, she should:

A. Hold the acidity of the water constant

B. Vary the temperature of the water used

C. control the final algae population sizes

D. use the same species of algae in all trials

A student conducted an experiment to determine if listening to different types of music would affect pulse rate. She thought that pulse rate would change with different types of music. Each person participating in her experiment listened to seven different selections of music for 30 seconds each. The pulse rates were taken after each 30-second interval of music. Based on her experiment, the student concluded that a person’s pulse rate changed when listening to different types of music.The component missing from this experiment is a

(1) prediction(2) hypothesis(3) control group(4) research plan