A study evaluates the effectiveness of a child abuse prevention program by comparing the rate of child abuse among parents who chose to participate in the program to the rate of parents who declined participation. This design fails to control for:
A) selection biases
B)correlation.
C)testing effects.
D) instrumentation changes
A school social worker administered a self-esteem test to a group of 9th graders in September. During the school year the students received intensive social work intervention designed to improve their self-esteem. In May the self-esteem test was given again and the self-esteem scores improved. Which of the following statements is true about this study?
A) It s results show that the intervention was effective in improving self esteem.
B)It only controls for testing effects and statistical regression.
C)It only controls for history and maturation.
D) It does not permit any conclusive causal inferences to be made.
Suppose a case management program is established to reduce rehospitalization rates in a hospital and that those rates drop dramatically once the new program is established. We can conclude that:
A) research has demonstrated an effective approach to practice.
B)causality cannot be inferred because time order was not established.
C)another event occurring during the time of the study might explain away the change.
D) the absence of covariation threatens the internal validity of any causal inferences.
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