In a true experimental design, which two characteristics are required?

In a true experimental design, which two characteristics are required?

• A. Random sampling and a treatment group
• B. Randomization and a control group
• C. Double-blind procedures and random sampling
• D. Random assignment of subjects to groups and a control or comparison group

Answer: (D)

The key idea being tested is how true experiments establish causality by controlling for differences between groups. In a true experimental design, you must randomly assign participants to distinct groups and include a control or comparison group. Random assignment makes the groups similar on average at the start, so any post-treatment differences are more likely due to the manipulated variable rather than preexisting differences. The control or comparison group provides a baseline to judge what would have happened without the treatment, allowing you to attribute observed effects to the intervention itself. Random sampling and double-blind procedures are valuable in other respects (generalizability and bias reduction, respectively) but are not required for a design to be considered a true experimental design.

The key idea being tested is how true experiments establish causality by controlling for differences between groups. In a true experimental design, you must randomly assign participants to distinct groups and include a control or comparison group. Random assignment makes the groups similar on average at the start, so any post-treatment differences are more likely due to the manipulated variable rather than preexisting differences. The control or comparison group provides a baseline to judge what would have happened without the treatment, allowing you to attribute observed effects to the intervention itself. Random sampling and double-blind procedures are valuable in other respects (generalizability and bias reduction, respectively) but are not required for a design to be considered a true experimental design.