Psychology / Unit 1: Introduction and Research Methods
1.4 Experiments and Variables
Notes
An experiment is the only method that can show cause and effect, because the researcher controls conditions.
- The independent variable (IV) is what the researcher changes. The dependent variable (DV) is what is measured.
- The experimental group gets the treatment; the control group does not.
- Random assignment puts participants into groups by chance so the groups start out similar.
- A placebo is a fake treatment. In a double-blind study, neither participants nor researchers know who got the real treatment, which reduces bias.
- Example: students are randomly assigned to sleep 5 or 9 hours, then take a memory test. IV: hours of sleep. DV: memory score.
Practice
In a study, one group drinks a new sports drink and another drinks plain water, and then both run a mile. The time to run the mile is the:
The DV is the outcome that is measured.
Why do researchers use random assignment?
Chance placement spreads individual differences evenly across groups.
In a double-blind study:
This reduces both participant expectations and researcher bias.
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