Control

Logic

Step 1: Selecting participants--How?

• random selection/sampling=everyone has an equal chance of being selected from the population into the sample.

















• defining your population

Step 2: Assigning Participants to groups--How?

• Elimination

• Equating

3. Counterbalancing=balancing of the order of treatment conditions

S1:Treatment 1	Treatment 2	Treatment 3
S2: Treatment 2	Treatment 3	Treatment 1
S3: Treatment 3	Treatment 2	Treatment 1

Experimental	Control
M1st	W1st
W2nd	M2nd
W3rd	M3rd
Wth	M4th

4. Random Assignment

Step 3: Design of Experiment

Recall:

Experimental

"Posttest only control group design"

Experimental	Control

Problems:

a. did randomization really work?

"Pretest-Posttest control group design"

Experimental	Control

Problems:

a. demand characteristics?

"Solomon 4 group design"

Experimental	Control
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