Text Explanation

Internal validity.: This answer choice is incorrect, because the internal validity of a study refers to whether or not there may be confounders within the study. For example, since preschoolers usually have their parents bring them to school, perhaps time spent with parents is what is truly predicting intelligence quotient rather than time spent in preschool. This critic is not concerned with the study's external validity.

External validity.: This answer choice is incorrect, because the external validity of a study refers to the degree to which the results of a study may be generalized (e.g. whether time spent in preschool correlates with intelligence in some other location as well as the location where the study was performed). The critic is not concerned with the study's external validity.

Statistical conclusion validity.: This answer choice is incorrect, because statistical conclusion validity refers to whether results are statistically significant enough to draw conclusions. For example, if you flip a coin twice and it lands on heads both times, you cannot conclude with statistical significance that the coin is rigged. However, if you flip a coin one thousand times and it lands on heads every time, your results are statistically significant. The critic of the study is not concerned with statistical significance.

Construct validity.: This answer choice is correct. Construct validity refers to how accurate each measured variable represents the conceptual variable. The conceptual variable in this case is intelligence, and the measured variable is IQ. The critic of the study is claiming that the IQ test used does not accurately reflect intelligence. In other words, the critic is objecting to the study's construct validity.