Final answer:
The classical experimental design includes random assignment, a control group, placebo treatment, and blinding. It differs from a one-group pretest posttest design by having a control group.
Step-by-step explanation:
The classical experimental design includes several components:
- Random assignment: Subjects are assigned randomly to different treatment groups to eliminate lurking variables.
- Control group: One group acts as a control group to demonstrate what happens when the active treatment is not applied.
- Placebo treatment: Participants in the control group receive a placebo treatment that looks exactly like the active treatments but cannot influence the response variable.
- Blinding: Both researchers and subjects may be blinded to preserve the integrity of the placebo.
A one-group pretest posttest design, on the other hand, does not have a control group. Instead, it involves administering a pretest to a group, applying the treatment, and then administering a posttest to measure the change. The lack of a control group makes it difficult to determine if the observed change is due to the treatment or other factors.