Which of the Following Factors or Situations in a Study

Which of the following factors or situations in a study using a correlational design should cause you to question the validity of the study?

A) The study did not have a nontreatment control group.
B) The researchers concluded that a causal relationship existed between the variables.
C) The researchers suggested that their findings had practical application in a clinical setting.
D) The researchers used preexisting instruments to measure the variables instead of developing specific instruments for the study.