Occupation and diet. Do various occupational groups differ in their diets? A British study of this question compared 98 drivers and 83 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).”45 Some of the study results appear below:

Drivers Conductors Total calories 2821 ± 44 2844 ± 48 Alcohol (grams) 0.24 ± 0.06 0.39 ± 0.11

(a) What does “se” stand for? Give x and s for each of the four sets of measurements.

(b) Is there significant evidence at the 5% level that conductors consume more calories per day than do drivers? Use a t test to give a P-value, and then assess significance.

(c) How significant is the observed difference in mean alcohol consumption? Use a t test to obtain the P-value.

(d) Use of the pooled two-sample t test is justified in part (b).

Explain why. Also find the P-value for the pooled t statistic and compare with your result in part (b).

(e) The report says that the distributions of alcohol consumption among the individuals studied are “grossly skew.” Do you think that this skewness prevents the use of the two-sample t test for equality of means? Explain your answer.