Table 1.

 Reporting of sample size calculations in trial protocols and publications

Component of sample size calculation	No of trials reporting each component (n=62)*
	Protocol	Publication	Both
Name of outcome measure	51	31	28
Minimum clinically important effect size (delta)	53	33	32
Estimated event rate in each study arm†	20/27	12/16	9/14
Standard deviation for delta‡	18/24	9/14	7/12
Alpha (type 1 error rate)	50	33	31
Power	51	34	32
Calculated sample size	62	30	30
All components reported	37	21	18

*Among trials reporting at least one component of sample size calculation in trial protocol.

†For trials reporting sample size calculations using binary outcome measures.

‡For trials reporting sample size calculations using continuous outcome measures.