This document defines and distinguishes between independent and dependent variables in scientific experiments. It states that independent variables are those that are intentionally manipulated or controlled, while dependent variables are simply measured and can vary at unknown rates in response to changes in the independent variable. Independent variables are represented on the x-axis and cause changes in the dependent variables, which are represented on the y-axis and reflect the effects or response. Examples are provided to illustrate these concepts.

1. Dependent v. Independent
Variables
What’s the difference?

2. What is a Variable?
 Simply, something that varies.
 Specifically, variables represent persons or
objects that can be manipulated, controlled, or
merely measured for the sake of research.
 Variation: How much a variable varies. Those
with little variation are called constants.

3. Independent Variables
 These variables are ones that are more or less
controlled.
 You might manipulate these variables as
needed.
 They still vary, but the variation is relatively
known (like seconds, or days)
 It is easy to figure the next independent
variable.

4. Dependent Variables
 Dependent variables are not controlled or
manipulated, but instead are simply
measured.
 Dependent Variables depend on what
the independent variable is.

5. Independent V. Dependent
 Intentionally manipulated
 Controlled
 Vary at known rate
 Cause
 Intentionally left alone
 Measured
 Vary at unknown rate
 Effect

6. Graphing Dependent v.
Independent Variables
Dependent
Variable
Independent Variable

7. Height of a ramp
(cm)
Time
to
roll
down
the
ramp
20
5 10 15 25
Example

8. Summary
 Independent is the x axis
 Independent is the x coordinate
 Dependent is the y axis
 Dependent is the y coordinate

9.  Orchids were studied to determine if the
amount of humidity affected the flowering of
these plants. Which of these was the
independent variable in this study?
 Amount of water
 Amount of humidity

10.  A soap manufacturer wants to
prove that their detergent works
better to remove tough stains.
What is the dependent
variable?
 Removal of stain
 Detergent

11.  You want to measure the effect of
different amounts of oxygen on the
rate of yeast growth. What is the
dependent variable?
 Amount of yeast growth
 Amount of oxygen

12.  Harvester ants often strip a bush of all of
its leaves. Some people believe this
helps the plant grow thicker, healthier
stems. In an experiment, a student
stripped off all the leaves from a set of
plants. In a second set of identical plants,
the student allowed ants to strip off the
plants’ leaves. In order to improve this
experimental design, it is most important
to add a set of plants —
 Plants with their leaves on
 With different types on them

13. An entomologist (bug scientist) wants to
determine if temperature changes how
many times a cricket chirps. What is the
dependent variable?
Number of crickets
temperature