Unit 2 Definitions #4

All 200 fifth graders at a school are randomly assigned to one of two groups. One group studies addition of fractions with the aid of a calculator, the other studies the same topic without a calculator. Scores on a fractions test are compared after two weeks.

• Observational Study

• Experiment

A researcher stood at a school parking lot entrance to see if the color of a car is related to the driver not wearing a seatbelt.

• Observational Study

• Experiment

A professor finds that people who are obese have higher cholesterol levels than those who are not obese.

• Observational Study

• Experiment

A researcher is interested in how caffeine affects sleep. He has 100 people spend the night in the lab. Before bed, he gives 50 people decaffeinated coffee and 50 people caffeinated coffee. He records the brain waves of each participant throughout the night. What kind of study is this?

• observational study

• experiment

Identify the independent variable in the following scenario: A scientist wants to test how the amount of sunlight affects the growth of plants.

• Temperature of the water

• Color of the plant pots

• Amount of sunlight

• Type of soil

Identify the independent variable in the following scenario: A student wants to investigate how the type of music affects a person's heart rate.

• Person's heart rate

• Type of music

• Time of day

• Weather conditions

Identify the dependent variable in the following scenario: A scientist wants to test how the amount of water given to plants affects their growth.

• Type of soil

• Temperature of the water

• Amount of sunlight

• Plant's growth

Identify the dependent variable in the following scenario: A student wants to investigate how the type of food affects a person's energy levels.

• Weather conditions

• Energy levels

• Person's age

• Type of food

Runners after an ultramarathon commonly develop respiratory infections. We want to know if taking 600 milligrams of vitamin C daily will reduce these infections. Researchers randomly assigned 100 ultramarathon runners to receive either vitamin C or placebo. All subjects were watched for 14 days after the big race to see if infections developed. The type of design used here?

• matched pairs
• randomized block
• completely randomized
• stratified 

In order to perform an experiment using 60 members of a gym, I first divide the list of members into men and women because I feel that the results will be different based on gender. I then randomly choose 30 men and 30 women. I assign half of the men to the treatment group and half to the control group. I repeat this procedure with the women. This is an example of a:

• randomized comparative design
• blocking design
• matched pairs design
• double blind simple random sample