A Canadian railway company claims that its trains block crossings no more than 5 minutes per train on the average. Passengers feel that this time is much longer. The actual times(minutes) that 10 randomly selected trains block crossings were:

9.3 9.7 6.5 9.5 8.8 11.2 7.2 10.5 8.2 10.4

The sample mean = 9.130 and sample variance = 2.209. In testing this claim, at the significance level of 0.05 and assuming that the crossing times are normally distributed, the critical value and the test statistic are, respectively:

a.
1.96 and 2.78

b.
1.8331 and 5.91

c.
2.2622 and 8.79

d.
2.2622 and 5.91

e.
1.8331 and 8.79

Find the sample size necessary in order to be 95% confident when determining the true mean weight within 2 units (E= 2). Assume that sample variance is 44.

a.
89

b.
65

c.
157

d.
43

e.
170