Unformatted text preview: y over a tenyear period than those who on average smoked at least 5. c. [4 points]
No, we cannot estimate the diﬀerence in the proportions who got lung cancer between those who smoked fewer than 5 cigarettes per day and those who smoked at least 5 per day. This is a retrospective study, so we do not know the population prevalence of lung cancer. These data may have been obtained from “samples of convenience” (whatever hospitals in several English cities had). We do not have information regarding how and when the data were collected. You may calculate the quantity according to the previous table: 1295 62 − = .246 − .526 = −.280 62 + 190 1295 + 1167 However, this quantity does not reﬂect the diﬀerence of the population proportions, and thus is not an estimate for the diﬀerence. Problem 2.8 [8 points]
a. [3 points]
Within row i, the odds that a subject would be in the lung cancer group instead of the control group is deﬁned to be: πcanceri Ωi = πcontroli Therefore, we can add the sample log odds for each level of smoking to the table: Daily Average Number of Cigarettes 0 <5 514 1524 2549 50+ Lung C...
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 Spring '12
 J.Kang
 Statistics

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