Question

Do various occupational groups differ in their diets? A British study of this question compared 95 drivers and 57 conductors of London double-decker buses. The conductors' jobs require more physical activity. The article reporting the study gives the data as "Mean daily consumption ± (se)." Some of the study results appear below. Drivers Conductors

Total calories 2828 ± 44 2842 ± 49

Alcohol (grams) 0.27 ± 0.06 0.44 ± 0.05

What justifies the use of the pooled two-sample t test?

The similarity of the sample means suggests that the population standard deviations are likely to be different.

The similarity of the sample standard deviations suggests that the population standard deviations are likely to be different.

The similarity of the sample means suggests that the population standard deviations are likely to be similar.

The similarity of the sample standard deviations suggests that the population standard deviations are likely to be similar.

Is there significant evidence at the 5% level that conductors consume more calories per day than do drivers? Use the pooled two-sample t test to obtain the P-value. (Give answers to 3 decimal places.)

t =

df =

P-value =

Answer 1

Let X1 shows the drivers and X2 shows the conductors. So we have

The similarity of the sample standard deviations suggests that the population standard deviations are likely to be similar.

t = -0.205

df = 150

P-value = 0.4189