A random sample of smokers was obtained, and each individual was classified both with re...

A random sample of smokers was obtained, and each individual was classified both with respect to gender and with respect to the age at which he/she first started smoking. The data in the accompanying table is consistent with summary results reported in the article “Cigarette Tar Yields in Relation to Mortality in the Cancer Prevention Study II Prospective Cohort” (British Med. J., 2004: 72–79).

a. Calculate the proportion of males in each age category, and then do the same for females. Based on these proportions, does it appear that there might be an association between gender and the age at which an individual first smokes?

b. Carry out a test of hypotheses to decide whether there is an association between the two factors.