Table 8.12 shows the 24 hour total energy expenditure of groups of lean and obese women. The aim of this study was to compare total energy expenditure between the lean and obese women.

(a) Write out a suitable null and alternative hypothesis for this problem and data.

(b) Do these data suggest that women in the lean group have a different total energy expenditure to women in the obese group? Stating any assumptions you make, perform an appropriate hypothesis test to compare mean 24 hour total energy expenditure (MJ/day) between the groups of lean and obese women. Comment on the results of this hypothesis test.

(c) Calculate a 95% CI for the difference in mean 24 hour total energy expenditure (MJ/day) between the groups of lean and obese women.
Discuss whether the confi dence interval suggests that women in the obese group might have higher total energy expenditure than women in the lean group.