{smcl}
{* 10 May 2022}{...}
{hline}
help for {hi:rdiff}
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{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}