Table 2.

Sample size calculations based on previously published studies

Definition of AAD	Control event rate (%)	Experimental event rate (%)	Sample size	Sample size including 20% lost to follow-up
≥3 loose or watery stools per day for a minimum of 48 hours during antibiotic treatment18	23	8	104+104	250
≥3 loose or watery stools per day for a minimum of 24 hours during antibiotic treatment22	28.3	11.8	104+104	250
≥2 loose or watery stools per day for a minimum of 24 hours during antibiotic treatment20	26	8	79+79	190

AAD, antibiotic-associated diarrhoea.