Table 1.

Statistical analysis of serological responses after smallpox vaccination

Days after Smallpox Vaccination	Average Percent Changea	Unadjusted P valueb	Significance Thresholdc	Significant?
7	6 (−4, 13)	0.18	0.010	No
14	8 (4, 14)	0.03	0.006	No
21	7 (2, 13)	0.07	0.007	No
33	7 (2, 8)	0.03	0.006	No
63	−2 (−16, 8)	0.75	0.050	No
125	6 (−3, 11)	0.18	0.008	No
181	4 (−7, 14)	0.45	0.017	No
287	2 (−10, 6)	0.66	0.025	No
371	5 (−3, 5)	0.26	0.013	No

^aThe average percent change from baseline values to the indicated time points after smallpox vaccination were determined for up to eight unrelated antibody titers in four subjects. The data are based on 30 individual ELISA measurements performed at each time point and the range in average percent change per individual is shown in parentheses.

^bUnadjusted P values were calculated by Student’s t-test prior to adjustment for multiple testing.

^cIn these studies, independent analyses were collectively performed to test a single hypothesis (i.e., change in pre-existing antibody level from baseline due to smallpox vaccination) and therefore multiple testing correction is required[9]. Multiple test significance thresholds were calculated using the Holm procedure and were based on an experimentwise α = 0.05 as described previously [1]. Data was ranked by the significance threshold and then placed in the table according to the time after smallpox vaccination. For comparison, a statistically significant value after the Bonferroni correction would be a P value of <0.006.