### Experimental Design

```Experimental Design
 Should be an
organized process,
used to test a
hypothesis
 Should test one
variable, with all
other variables
controlled
Controls and Variables
 Control—a factor that
does not change in an
experiment
 Independent Variable—A
variable that is not
changed by other things
that you are trying to
measure
 Dependent Variable—
Something that depends
on (or could be changed
by) other factors
Control Group
 a group of subjects in an experiment that are
not given any special treatment
 something that is not manipulated
 same as the experimental group in every
possible way, except for the factor being
tested
Example
The resting heart rate represented the baseline heart rate to
which any increase in activity level was compared to.
Constants
Factors in an experiment (both in the
experimental and control groups) that are
kept the same and not allowed to change

Examples
1.
One minute was consistently the amount of time allotted to
perform the necessary activity
2.
3.
4.
The type of activity performed
The stopwatch used during data collection
The method used to measure the heart rate
Identify the Variables
1.
independent
variable
If a student chooses to not study, then
they will earn a poor grade.
independent
dependent
variable
variable
2. If you drink Gatorade before a soccer
game, then you will score more dependent
goals.
variable
independent
variable
3. If you increase the mechanical advantage
of a pulley system used to move an
object, then the input force becomes
less.
dependent
variable
Data Collection
 Data should be
reported in a neat
table (rows and
columns)
 Units should have
their own spaces, not
listed with numbers
Substance
Density
Mass
Volume
g/mL
g
mL
A
0.5
50
100
B
1
450
450
Drawing Conclusions
 A conclusion is a
judgment based on
the results of an
experiment
 It should be based on
evidence and fact,
not merely opinion
Theories
 A theory must
explain
observations
clearly and
consistently.
 Theories can be
proven false in light
of new evidence.
 Theories can be
used to make
predictions
Scientific Law
 A concise statement
of a relationship or
conditions that are
always the same
 Ex. What goes up
always comes down
Models and Math
Math quantifies
science and gives
it meaning.
Scientific Models
give visual
representation of
physical events
```