With a Review of Identifying Variables
Identifying Variables Review
 Independent Variable – the variable that the scientist
will change to observe the effect
 Dependent Variable – the variable that the scientist
will measure and record - It’s the data of the
experiment
 Controlled – the variable(s) that the scientist
purposely keeps the same
Practice Identifying Variables
Do people that use cell phones while driving have more
automobile accidents?
 Independent Variable: use of cell phones while driving
 Dependent Variable: number of automobile accidents
Practice Identifying Variables
Do tomato plants raised with music grow more
tomatoes?
 Independent Variable: presence of music
 Dependent Variable: number of tomatoes grown
Practice Identifying Variables
Does regular exercise decrease the number of colds a
person becomes infected with?
 Independent Variable: frequency of exercise
 Dependent Variable: number of infections with cold
virus
You will need to write a hypothesis statement
any time you plan to test how two variables are
related (ie. conduct an experiment). But what is
a hypothesis?
What is a hypothesis?
 A statement that predicts something
 Must be testable and measureable
 Written as an “if” “then” statement
A Hypothesis is NOT…
 A question
 A statement that uses words like:
 Maybe
 Probably
 Might
Writing a Hypothesis
 A hypothesis simply combines the independent and
dependent variables into a prediction statement.
 If you know the independent and dependent variables,
writing a hypothesis statement is easy!
Writing a Hypothesis
 Simply insert the independent and dependent
variables into the following format:
If the _______IV_______ increases/decreases,
then the _______DV_______ increases/decreases.
 The independent variable is the “if” part of the
hypothesis and the dependent variable is the “then”
part.
 Use only “increases” OR “decreases” for each part of your
hypothesis statement.
Example Hypothesis Statement
Research Question: What effect does the amount of light
have on plant growth?
Independent Variable: amount of light
Dependent Variable: plant growth (height)
If the amount of light shined on a plant each day
increases, then the daily plant growth increases.
Example Hypothesis Statement
Research Question: What effect does sleep have on test
scores?
Independent Variable: amount of sleep
Dependent Variable: test scores
If the amount of sleep a student gets decreases, then
the average test score the student earns decreases.
Example Hypothesis Statement
Research Question: What effect does batting practice
have on a player’s batting average?
Independent Variable: batting practice
Dependent Variable: batting average
If the amount of batting practice increases, then the
player’s batting average increases.
Remember, identify the variables first, then plug the
IV and DV into the hypothesis statement format