PRACTICE -- INDEPENDENT AND DEPENDENT VARIABLES


Identify the population of interest, and the independent and dependent variables for each research situation described below.

a. A school psychologist wants to determine if a remedial reading course increases scores in reading comprehension for lower SES elementary age children. They are compared to a group receiving regular reading instruction.

Population of interest: 

Independent variable:

Dependent variable:

 

Answer Key for a.

 

b. A sample of adult drivers records auto gas consumption for two weeks. Then they are given a presentation and a brochure of energy-saving tips. After the presentation, they are asked to record the gasoline consumption of their automobiles.

Population of interest: 

Independent variable:

Dependent variable:

Answer key for b.

 

c. Researchers have developed a new filament for 60 watt light bulbs. A sample of the new light bulbs is plugged into a usage monitor at the laboratory, and the number of hours before burning out is recorded for each bulb. A sample of the old light bulbs is tested also.

Population of interest: 

Independent variable:

Dependent variable:

Answer key for c.

 

d. A psychologist is studying the effects of hormone levels on weight. Five randomly selected rats is given daily injections of a growth hormone. The control group is injected with saline solution. The weight of each rat is recorded daily for a month.

Population of interest: 

Independent variable:

Dependent variable:

Answer key for d.

 

e. A developmental psychologist would like to know how much difference there is in vocabulary development between 6-year old boys and 6-year old girls.

Population of interest: 

Independent variable:

Dependent variable:

Answer key for e.

 

f. A researcher is investigating the effects of room temperature on reaction time. A sample of adults are measured for reaction time in a 70 degree room. Another group is measured in a 95 degree room.

Population of interest:

 Independent variable:

Dependent variable:

Answer key for f.