Which of the following is a threat to internal validity?
a. Generalization b. Selection bias c. Statistical significance d. Sample size
The correct answer and explanation is:
The correct answer is b. Selection bias.
Explanation:
Internal validity refers to the degree to which the results of an experiment or study accurately reflect the relationship between the variables being tested, without being influenced by external factors or confounding variables. One of the primary threats to internal validity is selection bias.
Selection bias occurs when there is a systematic difference between the groups being compared in a study, which is not due to the variables being studied but instead arises from the way participants are selected or assigned to different groups. For instance, if participants are not randomly assigned to treatment and control groups, the differences observed in the outcomes may be due to pre-existing differences between the groups, rather than the effect of the treatment. This makes it difficult to draw valid conclusions about causality.
Generalization is not a threat to internal validity but rather pertains to external validity. External validity refers to the extent to which study results can be generalized to other settings, populations, or times. In contrast, selection bias affects internal validity because it distorts the study’s ability to attribute outcomes to the variables being tested, rather than to pre-existing differences among participants.
Statistical significance and sample size are not direct threats to internal validity, although they are crucial considerations in designing and interpreting studies. Statistical significance is a measure of whether the observed effects are likely to be due to chance, and sample size influences the power of the study to detect a true effect. However, these factors do not, by themselves, undermine the internal validity of a study. They can influence how confidently researchers interpret their findings, but threats like selection bias are more directly related to the accuracy and reliability of the causal conclusions drawn from the study.