PH 384: Introduction of Epidemiology:

Assignment 2 (100 points possible)

1. Here is an example of case-control study. You want to do a study to see if

SUCRALOSE (artificial sugar) is a risk factor for pancreatic cancer. You

assemble a sample of 1000 pancreatic cancer cases from a cancer registry

and 1000 controls (people without the disease) using random digit dialing. Of

the cases, 500 did not use SUCRALOSE; Of the controls, 800 did not use

SUCRALOSE.

Questions:

1) Construct contingency table.

2) Answer the following questions:

Of people who had SUCRALOSE, what is percentage of them had

pancreatic cancer?

Of people who do not take SUCRALOSE, what is percentage of them

had pancreatic cancer?

3) Calculate odds ratio

4) Interpret odds ratio

2. In 2005, an investigator drew a random 1000 sample of all adults without a

chronic disease in a community. At this time point, forty (40%) percent of

people without the disease had a particular exposure, which is fixed. Within

the next five years, 55 cases of the disease occurred in the study population,

and 40 of these cases were exposed. Assume steady state conditions and

that the exposure is not a prognostic factor for the disease.

Questions:

5) Construct contingency table.

6) Estimate relative risk of exposure

7) Interpret relative risk of exposure

8) Estimate the attributable risk to exposure

9) Estimate the population risk difference

3. WKU is trying to determine whether to screen students for disease x, which is

highly communicable and preventable. Preliminary data from a pilot test

showed the following results: Of the 1000 people who actually had disease x,

680 tested positive. Of the 3000 people without the disease, 400 tested

positive.

1

a. Complete a 2×2, then answer the following questions

b. What is the sensitivity of the screening test ?

c. What is the specificity of the screening test?

d. What is the PPV of the screening test?

e. What is the NPV of the screening test ?

f. Prove a summary for the screening test or do you consider this screening

test a good screening test? (Refer the summary in the slide 48 on lecture

notes from chapter 8&9)

2

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