1. Warm-up What makes an experiment a good one?
Write a hypothesis for the following scientific questions:
How does sunlight affect plant growth?
How does the distance between earth and a star affect the star’s brightness?
How does seafloor topography affect wave height?

2. Title: ___________ Research question: _________________
Hypothesis: _______________________
Manipulated/Independent Variable: __________________________________
Controlled Variables: _________________
Data: (Make a chart)
Conclusion: _______________________
(Please use complete sentences.)

3. Parts of an Experiment
NC SCOS Obj. 1.2

4. Controlled = Good!
Controlled Experiment – only one variable is tested (or changed by experimenter) at a time
WHY? So you can tell what variable is causing observed results

5. Variable – any factor that can change from trial to trial
vary = change
Ex. Height of dropper, type of dropper, side of penny, etc.

6. Parts of an Experiment Independent (or manipulated) variable
-- factor that is changed by experimenter
-- changed 1st, on x-axis
2. Dependent (or responding) variable
-- factor that is measured to show results
-- changes 2nd, on y-axis
Dependent
Independent

7. For any research question: How does (independent) affect (dependent)?
A. How does sunlight affect plant growth?
B. How does the distance between earth and a star affect the star’s brightness?
C. How does seafloor topography affect wave height?
I.V
D.V.
I.V
D.V.
I.V
D.V.

8. 3. Constants (or controlled variables) – factors that are kept the same
4. Control group – a group or trial that does not receive any treatment
-- a standard for comparison
-- the “normal” group

9. Practice
Sally decides to test how fertilizer affects tomato production.
She grows two tomato plants nearby in her garden so they have the same soil, water, and sunlight.
She applies fertilizer to plant A and none to plant B.
Each week, she measures the number of tomatoes each plant produces.