Selection bias is a threat to internal validity arising from failure to use
A) a control group.
B) counterbalancing across conditions.
C) reliable measuring instruments.
D) random assignment.

Question

Quizplus · Accepted Answer

Random assignment ensures that participants are assigned to conditions in a way that is not influenced by any pre-existing differences between them. Failure to use random assignment can lead to selection bias, as certain types of people may end up in one condition more so than the other, making it difficult to determine if any observed differences are due to the treatment or due to pre-existing differences between groups. The other choices listed (control group, counterbalancing, reliable measuring instruments) are all important for experimental design and internal validity, but do not specifically address the threat of selection bias.

Selection Bias Is a Threat to Internal Validity Arising from Failure