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Table 1 Minimum protective and harmful effects at 80% power

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

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