Transcript Parts of an Experiment

Experiments
NC SCOS Obj. 1.2
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 the observed results
• Variable – any factor that can change
from trial to trial
– vary = change
– Ex. Height of dropper, type of dropper, side of
penny, etc.
Parts of an Experiment
1. Independent (or manipulated) variable
-- factor that is changed by experimenter
-- changed 1st, on x-axis
Dependent
2. Dependent (or responding) variable
-- factor that is measured to show results
-- changes 2nd, on y-axis
Independent
For any research question:
How does (independent) affect
(dependent)?
I.V
A. How does sunlight affect plant
growth?
D.V.
I.V
B. How does the distance between earth
and a star affect the star’s brightness?
D.V.
I.V
C. How does seafloor topography affect
wave height?
D.V.
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
Practice
I.V.
• Sally decides to test how amount of fertilizer
affects tomato production.
D.V.
• She grows two tomato plants nearby in her
garden so they have the same soil, water, and
sunlight. Constants
• She applies fertilizer to plant A and none to
plant B. Control group
• Each week, she measures the number of
tomatoes each plant produces.