A Controlled
Experiment
Part of the scientific method
Variables
A factor that can change. A variable can change other
factors when it changes.
Examples of variables:
-Temperature
-Light
- Open vs. Closed container
-Location
-Time
-Elevation
-Pressure

Quantitative and Qualitative


A Quantitative Variable is one that is measured
using numbers. Examples: temperature is
measured in degrees, length can be measured in
centimeters.
A Qualitative variable is one that can not be
measured in numbers, but by its qualities. Such
as bright, clear, rough, smooth, pain.
Independent vs. Dependent
Variables


The dependent variable is a factor that changes
because the independent variable changes. However
the independent variable is not changed by the
dependent variable.
Example: Elevation and Boiling temperature of water.
The boiling temperature of water changes because of
changes in elevation. Changes in the boiling
temperature of water do not change elevation.
Graphing Variables

The Independent variable is always graphed on
the X axis.
The dependent variable is always graphed on
the Y axis.
Boiling Temperature of water
215
210
205
Degrees F

200
195
190
185
180
0
2000
4000
6000
8000
10000 12000 14000 16000
Feet above sea level
Hypothesis vs. Theory



Hypothesis is a testable
statement that can be
proven false.
Can be a prediction of
an outcome
Hypothesis can become
a theory once it is
supported by enough
evidence.



Theories are supported
by multiple observations
or experiments
A theory may be proven
false or modified when
more data is collected
Usually the lest
complicated explanations
Control
-A variable or factor that does not change in the
experiment. It remains constant.
In a Controlled experiment only one variable is
allowed to change at a time. Everything else
remains constant.
Francisco Redi & Spontaneous
Generation
OBSERVATIONS: Flies land on meat that is left uncovered. Maggots appear on the meat.
HYPOTHESIS: Flies produce maggots.
VARIABLES
Covered jars
Uncovered jars
Controlled Variables:
jars, type of meat,
location, temperature,
time
After several
days
Independent Variables:
gauze (keeps flies away from
meat)
Dependent Variable:
whether maggots
appear
Maggots appear
No maggots appear
CONCLUSION: Maggots form only when flies come in contact with meat.
Spontaneous generation of maggots did not occur.
Replicates


In an experiment multiple copies of the
experiment are done at the same time.
This is to ensure that the results are accurate
(true) and not due to a mistake, error or chance
event.
Treatments


Set of variables in the experiment that are the
same in each group of replicates.
2 Treatments
Covered
Uncovered