Identifying Variables in an Experiment
The factor or variable being investigated (or tested) is called the INDEPENDENT variable.
The factor or variable being measured is called the DEPENDENT variable (because it is dependent on the
experiment).
Directions: For each of the following hypotheses, identify the independent variable, the dependent
variable, and two variables that would need to be controlled (constants) in order to perform a fair test
(controlled experiment).
1. Fertilizer in soil increases flower production.
Independent Variable: THE FERTILIZER
Dependent Variable: THE FLOWER PRODUCTION
Two Controlled Variables: SAME TYPE OF FLOWER, SAME TYPE OF FERTILIZER (IF WE ARE TESTING THE
AMOUNT), AMOUNT OF WATER, LOCATION OF FLOWERS, AMOUNT OF SUNLIGHT, SAME TYPE OF
SOIL
2. Medicine A will reduce the incidence of headaches.
Independent Variable: WHETHER OR NOT YOU USE MEDICINE A/TYPE OF MEDICINE USED
Dependent Variable: NUMBER OF HEADACHES
Two Controlled Variables: SIMILAR AGE GROUP OF PEOPLE, SAME AMOUNT OF MEDICINE, AMOUNT
OF TIME, SAME ILLNESS.
3. If zinc tablets are taken, then the number of colds per year is reduced.
Independent Variable: WHETHER OR NOT YOU USE THE ZINC TABLETS/NUMB ER OF TABLETS TAKEN
Dependent Variable: NUMBER OF COLDS
Two Controlled Variables: SAME ILLNESS, SAME TIME (1 YEAR), AMOUNT OF PEOPLE
4. If water is present, then the number of bacteria in garbage bins increases.
Independent Variable: WHETHER OR NOT WATER IS PRESENT
Dependent Variable: NUMBER BACTERIA
Two Controlled Variables: SIZE OF GARBAGE BINS, SAME OUTSIDE CONDITIONS
5. Girls throw softballs further than boys.
Independent Variable: WHETHER IT’S A GIRL OR A BOY/GENDER
Dependent Variable: DISTANCE OF THE THROWN SOFTBALL
Two Controlled Variables: SAME TYPE/MASS OF SOFTBALL, SAME LOCATION.