## 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.