Understanding group A streptococcal pharyngitis and skin infections as causes of rheumatic fever: protocol for a prospective disease incidence study

Table 1 Minimum protective and harmful effects at 80% power

Assumed prevalence of factor in controls (%)	Min. Protective OR detectable	Min. Harmful OR detectable	Power
90	0.430	4.016	0.8
80	0.512	2.358	0.8
70	0.546	2.005	0.8
60	0.558	1.864	0.8
50	0.555	1.803	0.8
40	0.537	1.793	0.8
30	0.499	1.832	0.8
20	0.424	1.954	0.8
10	0.249	2.327	0.8

ISSN: 1471-2334