If X is the response time, we ask for P(X > 5). This equals 2. In the eighth row and sixth column of the table, we find that 1−Φ(0.75) = XXXXXXXXXXHence the answer is 1 − 0.2266 = XXXXXXXXXXBecause of...

If X is the response time, we ask for P(X > 5). This equals

2. In the eighth row and sixth column of the table, we find that 1−Φ(0.75) = 0.2266. Hence the answer is 1 − 0.2266 = 0.7734. Because of the symmetry of the probability density φ, half of the mass of a standard normal distribution lies on the negative axis. Hence for any number a > 0, it should be true that P(Z ≤ a) > P(Z ≤ 0) = 0.5.