Experimental Design

What Makes a Good Experiment?
There are several components of good
experimental design.
 Problem Statement
 Hypothesis
 Experiment
 Data Collection
 Conclusion

Example Experiment
The experiment we will
be looking at today is
called “Drink, Drive, and
Die”.
 It was a science fair
project by a student at
Ashdown Junior High
School in Ashdown,
Arkansas.

Problem Statement
The problem statement is the question
that is being answered by the
experiment.
 In “Drink, Drive, and Die”, the problem
statement is “Will drinking a small amount
of alcohol decrease your reaction time and
impair your ability to drive?”

Hypothesis
A hypothesis is an educated guess.
 Ex: “I believe, it will take at least one 12 oz
beer, to affect your reaction time and
impair your ability to drive.”
 His hypothesis is an “educated guess”
because of the research he had done on
amounts of alcohol.

Experiment
After you form your hypothesis, you
test it.
You must plan your experiment first.
You need to decide on the number of
replications, the control, and the
variable.

Replication
Replication is the repeating the
experiment to check for consistency
and accuracy.
 If possible, you should always repeat your
experiment at least once to be sure the
results are consistent and accurate.

Sample Size
Sample size is the number of repetitions
you do.
 Usually the bigger the sample size, the more
accurate your experiment is.
 Ex: If you wanted to find the mean (or
average) height of your classmates and you
measured the three shortest people, you
would not get a very accurate result. If you
measured all of your classmates, from the
shortest to the tallest, your result would be
more accurate.

Control
Your control in your experiment is
anything you use to provide a basis for
comparing results or checking their
accuracy; stays the same.
 Ex: In “Drink, Drive, and Die”, the control
was the “normal” reaction time. He
compared the other reaction times to this
control.

Variables
A variable is a measurable aspect of an
experiment that has different values
under different conditions.
 In “Drink, Drive, and Die”, the variables
were the different amounts of beer.

Data Collection
In order to collect good
data, you must be a good
observer.
You need to pay attention to
the things surrounding your
experiment.
After you collect your data,
you must display it.
 Ex: In “Drink, Drive, and Die”,
he displayed his data in a line
graph.

Conclusion
In order to form your conclusion, you
must analyze your data.
This means to look at it carefully and
decide whether or not your data
supports your hypothesis.
 Ex: In “Drink, Drive, and Die”, his
hypothesis was supported by his data.