1. Designing An Experiment Step by step
Steps in Designing an Experiment   Hypothesis Pick Population: Random Selection then Random Assignment. Operationalize the Variables Identify Independent and Dependent Variables. Look for Extraneous Variables Type of Experiment: Blind, Double Blind etc.. Gather Data Analyze Results Repeat            
Designing An
Experiment
Step by step

2. Let’s do an experiment
  • Hypothesis: The red pill will reduce anxiety.
• We operationalize the definition of anxiety to mean those whose doctors claim they suffer from anxiety.
• We find 100 people who fit the operationalized definition

3. • We randomly assign half the men to the experimental group and half the men to the control group. (Same with women). • I, the researcher, do not know which group will receive the medication and which will receive the placebo. That means this is a double-blind experiment. This will reduce experimenter bias.

4. The experimental group will receive the actual medication
The experimental group will receive the actual medication. The medication is called the independent variable.
• The control group will receive a sugar pill (the placebo).

5. • The research team will ask all participants to measure their level of anxiety on a scale from 1 to 10.
Anxiety is the dependent variable (what is measured).  

6. • The control group will usually report a decrease in anxiety even though they received no medicine. This is called the placebo effect.

7. • Now that the experiment phase is done, you must consider the confounding variables. This is the stuff that will screw up your experiment. Ex: what if the control group had a mean age much less than the experimental group? What if the 2 groups had a different percentage of women?

8. • Our original hypothesis was: the red pill will reduce anxiety by 40%
• Our original hypothesis was: the red pill will reduce anxiety by 40%. • Results: The experimental group reported a mean of 10% reduction in anxiety versus a 5% reduction for the control group. • Theory: After several replications, the medicine has no significant effect on anxiety.

9. Reliability and validity?
• A finding is reliable if it can be replicated. If subsequent studies show that the red pill reduces anxiety then the findings are reliable, thus supporting the hypothesis.

10. • A study is valid if it measures what it is supposed to measure
• A study is valid if it measures what it is supposed to measure. If our experiment measured hypertension instead of anxiety, then the test is invalid, even if it is reliable.