The following are the amounts of time, in minutes, that it took a random sample of 20 technicians to perform a certain task: 18.1, 20.3, 18.3, 15.6, 22.5, 16.8, 17.6, 16.9, 18.2, 17.0, 19.3, 16.5, 19.5, 18.6, 20.0, 18.8, 19.1, 17.5, 18.5, and 18.0. Assuming that this sample came from a sym-metrical continuous population, use the sign test at the 0.05 level of significance to test the null hypothesis that the mean of this population is 19.4 minutes against the alternative hypothesis that it is not 19.4 minutes. Perform the test using

(a) Table I;

(b) The normal approximation to the binomial distribution.