{smcl} {* *! version 1.0.0 21Aug2021}{...} {title:Title} {p2colset 5 18 19 2}{...} {p2col:{hi:loasampsi} {hline 2}} power and sample size analysis for limits of agreement (LOA) {p_end} {p2colreset}{...} {marker syntax}{...} {title:Syntax} {p 8 14 2} {cmd:loasampsi} {it: mu} {it: delta} , {opt sd(#)} [ {opt l:evel(#)} {opt p:ower(#)} {opt n(#)} ] {pstd} {it:mu} is mean of differences and {it:delta} is maximum allowable mean difference between the two measurement methods; {it:delta} must be larger than the LOA. {synoptset 15 tabbed}{...} {synopthdr} {synoptline} {synopt :{opt sd(#)}}specify the expected standard deviation of the sample differences; {cmd:sd() is required}{p_end} {synopt :{opt l:evel(#)}}set the confidence level; default is {cmd:level(95)}{p_end} {synopt :{opt p:ower(#)}}specify the desired power; {cmd:power()} cannot be specified together with {cmd:n()}{p_end} {synopt :{opt n(#)}}specify the desired sample size; {cmd:n()} cannot be specified together with {cmd:power()}{p_end} {synoptline} {p2colreset}{...} {p 4 6 2} {marker description}{...} {title:Description} {pstd} {opt loasampsi} computes sample size at a specified power, and power at a specified sample size, for Bland and Altman's (1986) limits of agreement (LOA) analysis, according to the method developed by Lu et al. (2016). {pstd} The results produced by {opt loasampsi} are identical to those produced by the {browse "https://ncss-wpengine.netdna-ssl.com/wp-content/themes/ncss/pdf/Procedures/PASS/Bland-Altman_Method_for_Assessing_Agreement_in_Method_Comparison_Studies.pdf":PASS Sample Size Software} and the R package {browse "https://github.com/nwisn/blandPower/":blandPower}. {title:Options} {p 4 8 2} {cmd:sd(}{it:#}{cmd:)} specifies the expecteded stardard deviation of the sample differences; {cmd:sd() is required}. {p 4 8 2} {cmd:level(}{it:#}{cmd:)} specifies the confidence level, as a percentage, for the limits of agreement. The default is {cmd:level(95)} or whatever is set by {helpb set level}. {p 4 8 2} {cmd:power(}{it:#}{cmd:)} specifies the desired power at which sample size is to be computed. The actual power derived from the analysis is reported in the output. {cmd:power()} cannot be specified together with {cmd:n()}. {p 4 8 2} {cmd:n(}{it:#}{cmd:)} specifies the desired sample size at which the power is to be computed. The actual power derived from the analysis is reported in the output. {cmd:n()} cannot be specified together with {cmd:power()}. {title:Examples} {pstd} {opt 1) Computing sample size:}{p_end} {pstd}Set the mean difference to 0.50, the delta to 7, the SD to 2.5, and power to 0.80. {p_end} {phang2}{cmd:. loasampsi .50 7, sd(2.5) power(0.80)}{p_end} {pstd} {opt 2) Computing power:}{p_end} {pstd}Same as above but we specify n = 70 to find power at that sample size. {p_end} {phang2}{cmd:. loasampsi .50 7, sd(2.5) n(70)}{p_end} {title:Acknowledgments} {p 4 4 2} I thank John Moran for testing this package. {marker results}{...} {title:Stored results} {pstd} {cmd:loasampsi} stores the following in {cmd:r()}: {synoptset 12 tabbed}{...} {p2col 5 14 18 2: Scalars}{p_end} {synopt:{cmd:r(mu)}}mean of differences {p_end} {synopt:{cmd:r(delta)}}maximum allowable difference{p_end} {synopt:{cmd:r(sd)}}standard deviation of the difference{p_end} {synopt:{cmd:r(level)}}confidence level{p_end} {synopt:{cmd:r(power)}}actual power for the computed sample size{p_end} {synopt:{cmd:r(n)}}computed sample size{p_end} {p2colreset}{...} {title:References} {p 4 8 2} Bland, J. M., and D. G. Altman. 1986. Statistical methods for assessing agreement between two methods of clinical measurement. {it:Lancet} I: 307-310.{p_end} {p 4 8 2} Lu, M. J.,Zhong, W. H., Liu, Y. X., Miao, H. Z., Li, Y. C. and M. H. Ji. 2016. Sample Size for assessing agreement between two methods of measurement by Bland-Altman method. {it:The International Journal of Biostatistics} Article 20150039. (Published online).{p_end} {marker citation}{title:Citation of {cmd:loasampsi}} {p 4 8 2}{cmd:loasampsi} is not an official Stata command. It is a free contribution to the research community, like a paper. Please cite it as such: {p_end} {p 4 8 2} Linden A. (2021). LOASAMPSI: Stata module to compute power and sample size for limits of agreement (LOA) analysis {title:Authors} {p 4 4 2} Ariel Linden{break} President, Linden Consulting Group, LLC{break} alinden@lindenconsulting.org{break} {title:Also see} {p 4 8 2} Online: {helpb rmloa} (if installed) {p_end}