Question

Suppose in a certain cohort study a researcher followed 360 college students who regularly smoked cigarettes, and 1200 college students who did not regularly smoke cigarettes. None of the subjects had peptic ulcers at the start of the study period. At the end of the study period, 90 of the smokers and 60 of the nonsmokers had at least one peptic ulcer. For simplicity, assume that none of the students died or left the study early. Also, assume the sample is representative of the population of college students in Nevada. Finally, suppose that 20% of college students in Nevada regularly smoke cigarettes.

1. In the smokers, what percentage of the risk for developing at least one peptic ulcer is directly attributable to smoking?

2. In the population of Nevada college students, what absolute amount of risk for developing at least one peptic ulcer is directly attributable to smoking?

3. In the population of Nevada college students, what percentage decrease in the risk for developing at least one peptic ulcer could be achieved by completely eliminating smoking?

Answer 1

In the study of peptic ulcers due to smoking in students, the provided information is,

Regular Smoker students are 360 in which 90 students have peptic ulcer

Non-smoker regularly students are 1200 in which 60 students have peptic ulcer

1) Regular Smoker students are 360 in which 90 students have peptic ulcer

I.e. 90/360 = 0.25

I.e. 25 % of the risk for developing at least one peptic ulcer is direct to the smoker.

2) 20 % students from Nevada college are the smoker.

i.e in the sample of 100 students, 20 students are the smokers.

then chances of the risk for developing at least one peptic ulcer is directly are,

= 20 * (25/100)

= 5

I.e from Nevada college 5% students have chances of the risk for developing at least one peptic ulcer

3) In Nevada college 20% student Smoker have 5% chances of the risk for developing at least one peptic ulcer is directly

I.e 95% students are safe from Nevada college (100-5)%

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