Question

Of the 286 attendees of the outdoor camp, 37 developed antibodies against SARS-CoV-2 during the summer. There were 471 attendees of the indoor camp. Of these, 85 developed antibodies. 4. (2pts.) Complete the 2x2 table below using the data provided above. 5. (2 pts.) Identify and calculate the appropriate measure of association. 6. (2 pts.) Statistical analysis found this association to be statistically significant. "Create" a 95% confidence interval for the measure of association in question #12 that is consistent with the association being statistically significant. NOTE: You do NOT need to calculate anything: simply make up a confidence interval that would be consistent with the measure found in question #5 and which demonstrates statistical significance).

Answer 1

4.

	Developed antibodies	Did not develop antibodies	Total
Outdoor Camp	37	249	286
Indoor camp	85	386	471
Total	122	635	757

5.

Measures of association:

	Developed antibodies	Did not develop antibodies	Total	Cumulative incidence
Outdoor Camp	37	249	286	37/286,ie, 12.93%
Indoor camp	85	386	471	85/386,ie, 18.04%
Total	122	635	757

a. Risk Ratio: Cumulative incidence of people who went to the outdoor camp/Cumulative incidence of people who went to the indoor camp = 18.04/12.93= 1.39, ie People who went to indoor camps had 1.39% the chance of developing antibodies.

b. Risk Difference:Cumulative incidence of people who went to the indoor camp-Cumulative incidence of people who went to the outdoor camp = 18.04-12.93= 5.11,ie, approximately 5 in 100 excess people developed antibodies by going to indoor camp.

6.

If we consider Risk Difference and build CI for a test using 95% confidence level:

Then 95% CI:

(Absolute sample risk difference) +- (value of statistic t at 95% level for two tailed test)* (SD of absolute risk difference)

We would use t test as we are doing difference of two statistics