Table 1.

Smallest effect sizes (odds ratios) detectable for the largest and smallest ethnic minority groups at 80 % power (with two sided 5 % significance levels), for exposures with a prevalence of 10, 20 and 50 % in the reference (white British) group

Primary care data source	N	Prevalence of outcome in white British group
White British	238,211	10 %	20 %	50 %
Smallest detectable odds ratio
Bangladeshi	93,143	1.03	1.02	1.01
Irish	13,459	1.08	1.05	1.03

Secondary care data source	N	Prevalence of outcome in white British group
white British	28,618	10 %	20 %	50 %
Smallest detectable odds ratio
‘Other’ white	4477	1.14	1.09	1.05
Indian	711	1.35	1.23	1.11