1. Designing an Experiment
(The important 6 steps)

2. Control The sample that remains the same. No conditions change;1
Control
The sample that remains the
same. No conditions change;
Used as a comparison.

3. Did you have one? What would it be?
If testing if marigolds have an allelopathic effect.??

4. Variable The condition that changes. What you are testing.2
Variable
The condition that changes.
What you are testing.
ONLY one variable!

5. Did you only “change” one thing?
What other factors may effect your data?
(how seed are clustered, folding/layering of paper towels, amount of water…..)

6. Independent Variable
The condition that the person/scientist is changing/ testing
Ex: if testing what is the best fertilizer of fertilizer A,B,C…Independent Variable is the type of fertilizer

7. Dependent Variable This is what is changing due to the
independent variable. It is the what
Data is going to be collected.
Ex: the height of the plants. This is
dependent on the type of fertilizer given.

8. Sample Size 3 How many of each sample will you
have. The more samples for each
condition the better, within reason.
You should at least have three.

9. How many samples did you have. (How many seeds in each bag
How many samples did you have? (How many seeds in each bag? How many bags per variable?)
What would be appropriate?
Did you average the samples if more than one?
Must have more than 1!!

10. Data to Collect What kind of data are you collecting…weight, measure…4
Data to Collect
What kind of data are you
collecting…weight, measure…
You should always have
quantitative data. Will the data
help support your hypothesis?

11. Did you collect appropriate data?

12. Constants With only one variable, all the other conditions of5
Constants
With only one variable, all
the other conditions of
your experiment remain
the same for all samples.

13. Was only ONE condition changed?
This one was not followed by most groups.
ALL conditions must be same except the one
being tested. Only solution type, not amount or number of seeds, for example.

14. Free of Biases You need to have the same treatment for all samples.6
Free of Biases
You need to have the same
treatment for all samples.
Be objective. DO not
favor one sample over the
other.

15. Homework Address each step and how you need
to change it or state what you did to
satisfy the requirement. ( in your
lab book)