Name: ______________________
Date: ______________
Period: ________
Read the following information about independent and dependent variables.
Variables are any of the factors that could change in a scientific investigation. A controlled scientific
investigation is designed so that only one factor is changed or manipulated. However, one or more
factors may be measured during an experiment. All other factors remain constant throughout the
experiment. Suppose that you wanted to conduct an experiment to see how the amount of water a plant
receives affects its growth. Your question could be: “What happens if I give different plants different
amounts of water?”
 The independent variable is the factor that you wish to test and that you manipulate or change
so that you identify its effects. When you use the “If … then … because … “ form to set up your
variables – the independent variable is found after the word if. In the example above, you are
intentionally changing the amount of water. Therefore, the amount of water given to the plants is
the independent variable.
 The dependent variable is the factor that you measure to gather results. It is expressed in your
experiment set up after the word then. In the example above, you are measuring plant growth.
Therefore, plant growth is the dependent variable.
Complete the following sentence:
If ____________________(variable), then _________________ (variable).
Identify the independent and dependent variable in each situation.
1. What is the effect of an object’s height on it potential energy? If you increase the height from
which a golf ball is dropped onto the flat surface of flour, then the resulting crater will be bigger,
because the golf ball will have more speed.
Independent: _____________________________________
Dependent: _______________________________________
2. What is the effect of surface area on evaporation? If you increase the amount of pieces into which
you cut saturated sponges, then those cut into smaller pieces will dry faster than those cut into
bigger pieces because the smaller pieces have more surface area.
Independent: _____________________________________
Dependent: _______________________________________
3. What is the effect of texting on students’ grades? If students spend more time per week taking selfies,
then they will have lower GPA’s than students who spend less time taking selfies, because the time spent
taking selfies will reduce the amount of time spent studying.
Independent: _____________________________________
Dependent: _______________________________________
4. If exposure to the sun increases, then the amount of sunburn will increase because ultraviolet
radiation from the sun causes sunburn.
Independent: _____________________________________
Dependent: _______________________________________
5. If greater amounts of salt are added to water, then the freezing point of the mixture will decrease
more, because salt water freezes below 0 C.
Independent: _____________________________________
Dependent: _______________________________________
6. Sponge Bob and his Bikini Bottom pals have been busy doing a little research. Read the description for
the experiment below and answer the question that follow.
Patty Power
Mr. Krabbs wants to make Bikini Bottom a nicer place to live. He has created a new sauce that he
thinks will reduce the production of body gas associated with eating crabby patties from the
Krusty Krab. He recruits 100 customers with a history of gas problems. He has 50 of them (Group
A) eat crabby patties with the new sauce. The other 50 (Group B) eat crabby patties with sauce
that looks just like new sauce, but is really just a mixture of mayonnaise and food coloring. Both
groups were told that they were getting the sauce that would reduce gas problems. Two hours
after eating the crabby patties, 30 customers in Group A reported having fewer gas problems and
8 customers in Group B reported having fewer gas problems.
If ___________________________, then _______________________________.
What is the independent variable?
What is the dependent variable?
Is this a fair test? How do you know?
What would Mr. Krabbs’ conclusion be?