{smcl} {* 10 May 2022}{...} {hline} help for {hi:rdiff} {hline} {title:Title} {pstd} {bf:rdiff} —— Calculating 95% confidence intervals for the differences of binomial proportions. {title:Syntax} {p 8 18 2} {cmd:rdiff} {it:#n1} {it:#succ1} {it:#n2} {it:#succ2} [{cmd:,} {opt c:orrect}] {title:Description} {pstd} {cmd:rdiff} is an immediate command that constructs a 95% confidence interval for the difference between two independent binomial proportions. Besides the most well-known method —— normal approximation method —— which may produce undesirable results in extreme cases, the more remarkable method, Wilson score method, is also available. Note that {cmd:rdiff} is recommended only for the case where the proportion of #succ1 for #n1 is equal to or greater than the proportion of #succ2 for #n2. {title:Options} {phang} {opt c:orrect} specifies with continuity correction when calculating. {title:Examples} {pstd} Suppose that sample A shows 23 'successes' among 30 subjects and sample B shows 9 'successes' among 30 subjects. Calculating the 95% confidence interval for the rate difference without continuity correction: {phang2} {bf:.rdiff 30 23 30 9} {pstd} or with continuity correction: {phang2} {bf:.rdiff 30 23 30 9, correct} {title:Stored results} {pstd} {cmd:rdiff} stores the following in {cmd:r()}: {synoptset 15 tabbed}{...} {p2col 5 15 19 2: Scalars}{p_end} {synopt:{cmd:r(rd)}}rate difference{p_end} {synopt:{cmd:r(ll_a)}}lower limit calculated by normal approximation method{p_end} {synopt:{cmd:r(ul_a)}}upper limit calculated by normal approximation method{p_end} {synopt:{cmd:r(ll_w)}}lower limit calculated by Wald score method{p_end} {synopt:{cmd:r(ul_w)}}upper limit calculated by Wald score method{p_end} {title:References} {phang} Beal, S. L. 1987. Asymptotic confidence intervals for the difference between two binomial parameters for use with small samples. {it:Biometrics}, 43: 941{c -}950. {phang} Newcombe, R. 1998. Interval estimation for the difference between independent proportions: Comparison of eleven methods. {it:Statistics in Medicine}, 17: 873{c -}890. {title:Author} {phang} {cmd:Xiaokun Yang}, Lanzhou University, China.{break} E-mail: {browse "mailto:yangxk19@lzu.edu.cn":yangxk19@lzu.edu.cn}.{break} {title:Also see} {phang2} Help: {help immed}, {help ci}, {help epitab}