Question

The main design-specific threat to the internal validity of a between-subjects design is a failure of random assignment. This is when the groups of subjects (assigned to the conditions) were not the same, on average, to start with. When this happens, you don't know if any difference in the data between conditions is due to the conditions or due to the pre-existing differences between subjects

Answer 1

The main threat to the internal validity of a between-subjects design is a failure of random assignment. Random assignment is important as it helps eliminate pre-existing differences between the groups and allows us to determine the effects of the conditions on the dependent variable.

Step-by-step explanation:

The main design-specific threat to the internal validity of a between-subjects design is a failure of random assignment. Random assignment is critical for sound experimental design as it makes it unlikely for systematic differences to exist between the groups. By randomly assigning subjects to different conditions, we can assume that any differences observed between the groups result from the manipulation of the independent variable. This helps us determine if the differences are due to the conditions or pre-existing differences between subjects.