The cost of a college education has increased at a much faster rate than costs in general over the past twenty years. In order to compensate for this, many students work part or full time in addition to attending classes. At one university, it is believed that the average hours students work per week exceeds 20. To test this at a significance level of 0.05, a random sample of n = 20 students was selected and the following values were observed.

26 15 10 40

10 20 30 36

40 0 5 10

20 32 16 12

40 36 10 0

Based on these sample data, which of the following statements is true?

a. The standard error of the sampling distribution is approximately 3.04.

b. The test statistic is approximately t = 0.13

c. The research hypothesis that the mean hours worked exceeds 20 is not supported by these sample data.

d. All of the above are true.