Probiotic supplementation decreases intestinal transit time: Meta-analysis of randomized controlled trials

Table 7 Sample size requirements for randomized controlled trials based on standardized mean difference

SMD	Study design
	Parallel groups1	Cross-over
0.2	786	156
0.3	350	71
0.4	198	41
0.5	128	27
0.6	90	19
0.7	66	15
0.8	52	12

¹Total sample size, assuming 1:1 active-to-control group ratio. Assumes two-sided alpha of 0.05 and statistical power of 80%. Attrition estimate not included. SMD: Standardized mean difference.