Designing an Experiment

O-H-E-C-C

Determining a Purpose

Do researchExamine results of a previous experimentObserve the world around you

ExperimentAn organized procedure to study something under controlled conditions.

PurposeWrite the purpose of your experiment as a question or problem that you want to investigateWrite down research questions and begin searching for information that will help you design an experiment. Consult the library, internet, and other

people

Example What is Gary’s purpose of this experiment?Gary observed that he seems to be able to concentrate more and seems smarter after he eats Super Snail Snacks. He also noticed that his friend Barry also had experienced the same effects. Gary and Barry did some research to learn more about their observations. They discovered that the Super Snail snacks may be associated with increased brain function. Gary is not the smartest snail in Bikini Bottom and believes he can improve his brain power by eating Super Snail Snacks. He decided to design a controlled experiment to find out whether they were right.

Example cont.

How do Super Snail Snacks affect brain powerResearch Questions: Have other experiments been done

on this problem? If so, what did those experiments show?

How do people measure brain power?

Writing the Hypothesis

If the Super Snail Snacks are eaten, then Gary’s test scores will increase because they improve brain function.

Determining Materials

Materials Super Snail Snacks 2,000 Snails Pre-tests Post-tests Placebo snacks Marker ruler

Determing Variables and Constants

Variable is any factor that can changeConstants are all of the factors that are the same in both the experimental group and the control group

Experimental Group

Include as many trials as possible in the experimental group in order to obtain reliable resultsIn order to test this hypothesis, he recruits SpongeBob and several snail friends to help him with the experiment. 1,000 snails ate one Super Snail Snack with each meal every day for three weeks. SpongeBob created a test and gave it to the snails before they started eating the snacks as well as after three weeks.

Control Group Design a control group that is the same as the experimental group in every way possible, except for the factor you wish to test.1,000 snails ate one placebo snack with each meal every day for three weeks. SpongeBob created a test and gave it to the snails before they started eating the snacks as well as after three weeks.

Independent Variable

The factor that you wish to testEx) Super Snail Snacks

Dependent Variable

The factor that you measure to gather results.Ex) Test Scores

Operational DefinitionA description of the one particular way in which you will measure the dependent variableEx) Eating Super Snail Snack – Independent variablePercentage on Tests – dependent variable*Percentage of test scores after eating Super Snail Snacks*

Writing a ProcedureProcedure:1. Take a IQ pre-test.2. Divide snails into two groups.3. Give one group one snail

snack with each meal every day for three weeks.

4. Give the other group one placebo snack with each meal every day for three weeks.

5. Give each snail a IQ post-test.

Recording Observations

Once you have obtained all of your materials and your procedure has been approved, you can begin making experimental observations. Gather both quantitative and qualitative data. If something goes wrong during your procedure, make sure you record that too.

Summarizing Results

Test Results

Snail Before After

Gary 64% 80%

Larry 78% 78%

Barry 84% 84%

Terry 72% 70%

Drawing Conclusions

To draw conclusions from your experiment, first write your results. Then compare your results with your hypothesis. Do your results support your hypothesis? Be careful not to make inferences about factors that you did not test.

Results and Inferences

The results of my experiment show that some of the snails benefited from the Super Snail Snacks, but most did not. My hypothesis was not supported. I infer that it is not possible to improve brain function by eating Super Snail Snacks.

Questions for Further Research

Could the gains shown by some of the snails have been due to other factors?

Communicate the Results

Write a Lab Report