What makes an experiment
“fair”?
Variables in Science Experiments
**Make sure your hw is out**
Do Now:
Time: 3 minutes
Review: Using this scenario, write a
scientific question:
Belle notices that her blue bird feeder is
more empty than
her red bird
feeder after a few days. (Use one of the
question outlines I gave you to help you!)
Variables


A variable is something that can be changed
in an experiment.
A constant, or control, is something that does
not change in an experiment
Science experiments use…
**When you finish your notes, start thinking back to the
Do Now. Think about what would be the independent
variable in that experiment. What are you changing?**




Independent Variable: the one factor that is
changed by the person doing the experiment
Dependent Variable: the factor which is measured
in the experiment
Control: all the factors the scientist keeps the same
during the experiment
Constants: all factors that can NEVER change
A birdy example…
Imagine you want to see what color of bird
feeders your local birds preferred.
Red?
Blue?
Green?
Remind me of a good scientific question??
Our Constants and Variables



Independent Variable: Color of bird feeder
Dependent Variable: Amount of food eaten
Constants: everything else that is kept the same,
for example:
–
–
–
the location of the feeders
the kind of feeder used
putting the feeders out at the same time
Copy this table into your notebook!
Our Experimental Design
Controls
Independent
Variable
Dependent
Variable
If everything except the
independent variable is held the
same, we can say:
The experiment is FAIR.
(ONLY the independent
variable can change!)
Why is it important to only change
the independent variable?
Think-Pair-Share
Time: 1 minute
Discuss with the person next to you the
above question.
If you don’t…
You could get unreliable results! Only one
thing can be different; if more than one thing
is different, then you do not really know what
is causing the change in your
data!
Independent Variable
Is Sam’s experiment fair?
YES? NO?
NO! It isn’t fair since the locations of the
feeders were very different!
Is Maria’s experiment fair?
YES? NO?
YES! It seems fair since Maria only changed
the feeder color!
Is Jessie’s experiment fair?
YES? NO?
Monday
Tuesday
Thursday
NO! It isn’t fair since the feeders are not
out at the same time, and we know that
the weather was quite different each
time. Perhaps the number and kind of
birds that visited during the weeks were
different due to the weather.
What do you think?
Terry loves birds and wants to see as many as
she can in her yard. She wants to know
whether she is wasting money buying an
expensive mixed seed, when a cheaper brand
just arrived at her local store. She wonders…
will the expensive seed attract more birds to
her back yard?
How would you advise
her to find out if the
expensive seed is better?
Terry’s Experimental Design
Independent
Variable
?
Dependent
Variable
?
Constants
?
Terry’s Experimental Design
Independent
Variable
Kind of seed:
Expensive Cheap
Dependent
Variable
Number of birds that visit
Constants

Location of feeders
Type of feeder
Way she measures the amount of
seed eaten and the way she counts
birds
$
Classwork
Do the first question on your worksheet. If
you finish it before the time is up, move on
to the next question. Be ready to share out
your answers to question 1 with the class.
Refer back to your definitions of variables &
the examples if you need help!! You may
discuss the answers with the classmates
around you.
Time: 3 minutes
Classwork/Homework:
7th – Finish Simpsons variables
worksheet
8th – Finish Spongebob variables
worksheet