Section 1: Illustrating Experimental Research

Read the following scenario about an experiment being conducted to test which of two toothpastes works best at preventing cavities, and answer the questions that follow the scenario.

As a research director at Toothpaste International, I have recently completed experimental research to determine which toothpaste, Brand X or Brand Y, works best at preventing cavities.

For setting up my experiment I will ask twenty college students found on the NIACC campus if they would want to be part of a research design for six months to serve as my sample. The participation of NIACC students is entirely voluntary.

The participants will be required to be between the ages of 18 and 25 years with the requirements of having a dental record showing no current cavities. This will be determined by each participant visiting a dentist for an examination. If any of the initial participants show cavities, they will be replaced with another volunteer on campus.

Ten of the people will use (unknowingly) Brand X and the other ten people will use Brand Y. Since this will be a double-blind procedure neither the participants, nor the administer of the toothpaste, know which brand is received.

Why might a double-blind procedure be important?

Participants in each group will be provided instructions that include the following:

1. Use a pea size amount of toothpaste on the provided toothbrush.
2. Brush teeth both morning and night.

What is the hypothesis of this experiment?What is the independent variable?What is the dependent variable?

In my haste to begin the experiment, I may have inadvertently forgotten some extraneous (confounding) variables that must be controlled to ensure the results are valid.

Name at least 3 confounding variables and how they may affect the validity of results.

1.

2.

3.

At the end of 6 months, the participants visited the same dentist for another dental exam to determine cavity formation. It was found that 1 participant from the group using Brand X and 1 person from the group using Brand Y each developed 1 cavity. The results of this experiment did not show any statistical significance in determining which toothpaste works best at preventing cavities. More experimentation is needed to determine if the results are reliable.

Explain the concepts of reliability and validity in reference to experimental results and explain why they are important in research.

Section 2: Experimental Variables

Now that you've had some practice with an experiment, read the following scenarios and name the independent and dependent variables for each.

Scenario 1:

A biology teacher decided to use his own back yard and several students in his class to test the effectiveness of using a home-grown compost on his garden rather than using no compost. Half the students tended 1/2 the garden and used the compost, while the other half of the class tended to the other half of the garden without the use of compost. They had planted tomatoes in the garden and then watched them grow to see if tomatoes grew best in soil with compost or natural soil.

Independent variable:

Dependent variable:

Scenario 2:

Two groups of mice were run through a maze. The length of time it took to complete the maze of each mouse was recorded. One group of mice were given a sugar water to drink before they were run through the maze, while the other group was not.

Independent variable:

Dependent variable:

Scenario 3:

A psychology instructor decided to allow her students to listen to soothing music during the exam. Her first class listened to the soothing music but then the instructor could not get her iPod to work for the 2nd section of the course, so they were not able to listen to the soothing music. The psychology instructor thought it would be interesting to see if, on average, the students in the class that listened to the music scores higher on the exam than the class that did not listen to the music.

Independent variable:

Dependent variable:

Scenario 4:

A fitness center wanted to test a new workout on its members to see if it helped to lower their resting heart rate after completing the workout 3 days per week for 1 month. Some members were interested in trying the workout, while other members wanted to continue with their normal workout routine.

Independent variable:

Dependent variable:

Scenario 5:

A local food grower selling fruit at the farmers' market claimed that the vitamins in his strawberries can reduce age-related declines in cognitive functioning. A psychologist happened to overhear this claim and decided it would be interesting to try an experiment. Of 20 individuals, he asked the farmer to supply 10 of them with his strawberries, as the experimental group. Tests of cognitive functioning were given before and after the 4 month experiment.

Independent variable:

Dependent variable: