Confidence intervals for means
ci varname [if exp], exposure(varname) [level(#) format(format) bygroup(varname) per(1, 10, 100, 1000, 10000, 100000) outcome(description) group(description) col1(number) col2(number)]
Description
ndbci computes rates and Poison confidence intervals for a single variable. In contrast to Stata's ci, ndbci calculates rates and confidence intervals for each level of a grouping variable. ndbci allows formatting of the output and naming of the group and outcome variables. ndbci also formats output for 1, 10, 100, 1000, 10000 and 100000 person years.
Options
level(#) specifies the confidence level, in percent, for confidence intervals; see help level.
exposure(varname) is required. varname contains the total exposure (typically a time or an area) during which the number of events recorded in varname were observed.
per(1, 10, 100, 1000, 10000, 100000) person years. 1 year is the default value, assuming exposure is calculated in years.
outcome(description) is an optional name or phrase to replace dependent variable name. Default is to use the dependent variable name.
bygroup(grouping variable) requests an analysis for each level of the grouping variable.
format(format) formats output. Default format is 9.2f.
group(optional description for grouping variable) adds a description to the display in place of the grouping variable name.
col1(number) adds or subtracts (-) spaces just before exposure to aid in proper placement of the output. Default is 0.
col2(number) adds or subtracts spaces just before rate to aid in proper placement of the output. Default is 0.
Examples
. ndbci cycl if lpuse, exposure(_ndbtime) per(100000)
Years 100000 yr --Poisson Exact -- Outcome | Group Count Exposure Rate [95% Conf. Interval] -------------+--------------------------------------------------------------- cyclospr | All 189 26316.50 718.18 619.44 828.19
. ndbci cycl if lpuse, exposure (_ndbtime) bygroup(edcat) level(90) /// per(1000) outcome(Vanquished) format(%9.1f) group(Education) col2(-3) col > 1(-1) Years 1000 yr --Poisson Exact -- Outcome | Education Count Exposure Rate [90% Conf. Interval] -------------+--------------------------------------------------------------- Vanquished | 0-8 4 784.0 5.1 1.7 11.7 Vanquished | 8-11 12 2274.0 5.3 3.0 8.5 Vanquished | 12 56 9335.0 6.0 4.7 7.5 Vanquished | 13-15 54 6608.5 8.2 6.4 10.3 Vanquished | 16 or > 58 6819.0 8.5 6.8 10.6
Acknowledgement
This ado file is a partial wrapper for Stata's ci.
Also see
Manual: [R] ci
Online: help for ci
Author Fred Wolfe fwolfe@arthritis-research.org