Three persons (denoted A, B, and C) claiming to have unusual psychic ability underwent ESP tests at an eastern U.S. psychic research institute. On each of five randomly selected days, each person was asked to specify for 26 pairs of cards whether both cards in a given pair were of the same color or not. The numbers of correct answers are given in the accompanying table.

a. Determine the mean score for each person, and interpret the results.
b. Test whether the three persons have significantly different ESP ability.
c. Carry out Scheffe's multiple-comparison procedure to determine which pairs of persons, if any, significantly differ in ESP ability.
d. On the basis of the results in parts (b) and (c), can one conclude that any of these persons has statistically significant ESP ability? Explain.