Dr. Fredericks believes that environment is more important than genetics in influencing intelligence. He locates 12 pairs of identical twins that have been reared apart, one twin in each pair in an enriched environment and the other in an impoverished environment. He administers a standardized IQ test and obtains the results given in Data 15B.
(a) State formally the null and alternative hypotheses necessary to conduct a non directional test.
(b) Complete the test at the .05 level of significance, and state your conclusion.
(c) Why is this a dependent-samples design?
(d) Can Dr. Fredericks conclude that environment is more important than genetics from the results of this test? Explain.
(e) Calculate effect size, g.
(f) Could Dr. Fredericks really have obtained the 12 pairs of twins at random? What effect might this violation of one of the assumptions have on the outcome?