14.In a study of the effect of color on productivity，50 of 100 factory workers were moved from their drab workroom to a brightly colored workroom.Both these workers and the 50 who remained in the drab workroom increased their prod-uctivity， probably as a result of the interest taken by researchers in the work of both groups during the study.Which of the following， if true， would cast most doubt upon the author's inter-pretation of the study results given above?
(A) The 50 workers moved to the brightly colored room performed precisely the same manufacturing task as the workers who remained in the drab workroom.
(B) The drab workroom was designed to provide adequate space for at most 65 workers.
(C) The 50 workers who moved to the brightly colored workroom were matched as closely as possible in age and level of training to the 50 workers who remained in the drab work-room.
(D) Nearly all the workers in both groups had volunteered to move to the brightly colored workroom.
(E) Many of the workers who moved to the brightly colored workroom reported that they liked the drab workroom as well as or better than they liked the brightly colored workroom.
15.A researcher discovered that people who have low levels of immune-system activity tend to score much lower on tests of mental health than do people with normal or high immune-system activity. The researcher concluded from this experiment that the immune system protects against mental illness as well as against physical disease.
The researcher's conclusion would be most seriously weakened if it were true that
(A) there was a one-year delay between the completion of a pilot study for the experiment and the initiation of the experiment itself.
(B) people's levels of immune-system activity are not affected by their use of medications.
(C) a few people with high immune-system activity had scores on the test of mental health that were similar to the scores of people who had normal immune-system activity.
(D) people who have low immune-system activtiy tend to contract more viral infections than do people with normal or high immune-system activitiy.
(E) high levels of stress first cause mental illness and then cause decreased immune-system activitiy in normal individuals