Name: __________________________
Date: ________________________
Identifying Variables - Homework
Directions: For each experimental scenario, identify the independent variable, dependent variable and constants
1. Dr. Douglas read an article in a teacher’s magazine that said that students who read for at least fifteen
minutes every day score better on literacy tests than those who do not. Since she has to prepare her
students for the literacy test, she decides to test this idea on her students. In her first, second, and third
period class, she has the students read for the first fifteen minutes of the period. In her fifth, sixth, and
seventh period classes, the students spend that time writing instead. All of the students either read the
same books or write on the same topics during that time, and nothing other than the reading is different
between the two sets of classes.
Independent variable:
Dependent variable:
Constants:
2. A group of researchers want to test the effectiveness of new asthma medication for young adults. They
recruit 100 18 and 19-year-olds to test the medication and split them into 2 groups. Each group has 25
young men and 25 young women in it. One of the groups is given the new medication, while the other
group is given a sugar pill instead. Both groups take the pill once a day for a month and record how often
they experience asthma symptoms and/or have to use their inhalers.
Independent variable:
Dependent variable:
Constants variable:
3. The zoology class reads in its textbook that the gender of alligator babies is determined by the temperature
that the eggs are kept at. Their teacher locates some alligator eggs so the class can determine if this is a
true statement. They build two alligator nests and use heat lamps to heat the eggs in the nest. They put
half the eggs in one nest and heat it to 84º F. The other half of the eggs go in the other nest, which is heated
to 88º F. When the eggs hatch a few weeks later, they count the number of males and females in each nest.
Independent variable:
Dependent variable:
Constants variable:
4. Ahmad hears one of his teachers say that she plays classical music to her plants to help them grow. He goes
home and sets up his own experiment. He takes four pots of geraniums and sets them on his porch. Once a
day, he brings each pot inside for twenty minutes. He plays rap music for one pot, rock music to another
pot, and classical music to the third. One of the pots does not have any music played for it. Each day he
measures the growth of the geraniums. All the plants receive the same amount of water and daylight.
Independent variable:
Dependent variable:
Constants variable:
5. One time when Dr. Douglas went to the grocery store she bought all the types of microwave popcorn that
the store had. With these types of popcorn she conducted an experiment to see which type of popcorn
pops the most kernels. She put each bag into the microwave for 1 minute (each bag was the same size).
Then she counted the number of kernels popped in each bag and compared her results.
Independent variable:
Dependent variable:
Contants variable:
6. Tyra proposes the idea that a marble will travel at a faster pace if it is rolled down a steeper slide. This
discussion leads to the following scientific question. What happens to the speed a marble travels when the
height of a ramp is changed? Tyra decided to test her question by setting up three different slides of
various heights. She then took a marble and let it to roll down each slide. She recorded the time it took the
marble to reach the bottom. Each slide was made of the same material and the same marble was used on
each of the different slides.
Independent variable:
Dependent variable:
Constants variable:
7. Eric wants to determine the best temperature for storing batteries so that they will last the longest amount
of time possible. He takes three batteries that are the same size and same brand and stores each one in a
different location for a month. He places one in the refrigerator, one next to a heater, and one on a shelf at
room temperature. Then he takes each battery and puts it in a flashlight and leaves the flashlight on until it
dies. He records how long the batteries last in each flashlight.
Independent variable:
Dependent variable:
Constants variable:
Spot the error: Read the following experiments. Each experimental design has an error and it is
your job to identify this error and correct it! (Hint: start by identifying the variables)
1. Dimilah is studying the effect of sleep on aggression in humans and animals. She thinks that less sleep
will lead to more aggression. She has some cats sleep 6 hours per night and some dogs sleep 3 hours
per night and some people sleep as much as they want. She then monitors aggressive their aggressive
behavior and compares them.
 Independent Variable: _____________________________________________________________________________

Dependent Variable: _______________________________________________________________________________

Constants: ____________________________________________________________________________________________
What’s the problem with this experiment? Why is it a problem?_________________________________________________
_________________________________________________________________________________________________________________________
_________________________________________________________________________________________________________________________
_________________________________________________________________________________________________________________________
_________________________________________________________________________________________________________________________
_________________________________________________________________________________________________________________________
2. Tyrell keeps aquarium fish as pets. Last week, all of the fish in the glass aquarium died. He thought it
was because they were allergic to the glass. When Tyrell bought more fish, he decided to use a plastic
aquarium, a different type of fish food and a different temperature setting for the water. All of the new
fish survived.
 Independent Variable: _____________________________________________________________________________

Dependent Variable: _______________________________________________________________________________

Constants: ____________________________________________________________________________________________
What’s the problem with this experiment? Why is it a problem?_________________________________________________
_________________________________________________________________________________________________________________________
_________________________________________________________________________________________________
_________________________________________________________________________________________________________________________
_________________________________________________________________________________________________________________________
_________________________________________________________________________________________________________________________