3. Variables
In any experiment there are 3 variables:
An independent (changed) variable
A dependent (measured) variable
Some control variables
Let’s look at each type…
4. Independent Variable
This is the thing you decide to change
eg. Investigating how plants grow when they
are given different amounts of water
You change the amount of water you give the
plant.
So, amount of water is the independent
variable.
5. Dependent Variable
This is the thing that changes as a result.
This is the thing you measure
eg. Investigating how plants grow when they
are given different amounts of water
You measure how much the plant grows.
So, amount of growth is the dependent
variable.
6. Control Variables
These are all the things that must not change to
make it a fair test. They must be kept the same.
You need to keep the plants in the same place so
that they get the same amount of sunlight or shade.
You need to grow the plants in the same type of pot,
that are the same size.
The plants need to have the same type and same
amount of potting mix.
These are the control variables.
7. Summary
The independent variable is changed.
Amount of water
The dependent variable is measured.
Growth of plant.
The control variables are kept the same.
Amount of sunlight or shade.
Type of pot.
Size of pot.
Type of potting mix, etc.
9. Change one thing,
Measure one thing (usually),
Keep everything else the same.
10. Time For A Joke...
A Magician was
driving down the Q. What do u call a
road... guy with no shins?
then he turned into a
drive way... Tony
hahahahahahahahahah
12. Accuracy
The exactness or precision of a
measurement; relating to the degree of
precision in measurement.
Highly dependant on equipment choice to
measure values accurately
13. Reliability
• The degree with which repeated
observation and/or measurements taken
under identical circumstances will give the
same results.
14. Validity
The extent to which the processes and resultant
data measure what was intended.
Are the measurements you recorded caused by
the variables you think.
15. Reliability Have I tested with repetition?
Have I chosen equipment that will give
Accuracy me accurate and precise readings?
Does my experiment actually test the
hypothesis that I want it to? What
Validity variables have I identified and
controlled?
