Is reaction time to a red light different from that to a green light? Suppose 20 subjects have been selected at random and given a preliminary test to determine the reaction time of each individual to a white light stimulus. From among this group, 10 pairs of subjects are formed such that the two members of any given pair are equal or nearly equal in speed of reaction to white light. Taking each pair in turn, one member is first tested with a green light as the stimulus and the other with a red light. Which member of each pair receives which stimulus first is determined at random. Reaction times are recorded in milliseconds. The results are given in Data 15A.

(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) Does it matter which group was designated as X and which as Y?

(d) Calculate effect size, g.