Stata 15 help for stci

[ST] stci -- Confidence intervals for means and percentiles of survival time

Syntax

stci [if] [in] [, options]

options Description ------------------------------------------------------------------------- Main by(varlist) perform separate calculations for each group of varlist median calculate median survival times; the default rmean calculate mean survival time restricted to longest follow-up time emean calculate the mean survival time by exponentially extending the survival curve to zero p(#) compute the # percentile of survival times ccorr calculate the standard error for rmean using a continuity correction noshow do not show st setting information dd(#) set maximum number of decimal digits to report level(#) set confidence level; default is level(95) graph plot exponentially extended survivor function tmax(#) set maximum analysis time of # to be plotted

Plot cline_options affect rendition of the plotted lines

Add plots addplot(plot) add other plots to the generated graph

Y axis, X axis, Titles, Legend, Overall twoway_options any options other than by() documented in [G-3] twoway_options ------------------------------------------------------------------------- You must stset your data before using stci; see [ST] stset. by is allowed; see [D] by.

Menu

Statistics > Survival analysis > Summary statistics, tests, and tables > CIs for means and percentiles of survival time

Description

stci computes means and percentiles of survival time, standard errors, and confidence intervals. For multiple-event data, survival time is the time until a failure.

stci can be used with single- or multiple-record or single- or multiple-failure st data.

Options

+------+ ----+ Main +-------------------------------------------------------------

by(varlist) specifies that separate calculations be made for each group identified by equal values of the variables in varlist, resulting in separate summaries and an overall total. varlist may contain any number of variables, each of which may be string or numeric.

median specifies median survival times. This is the default.

rmean and emean specify mean survival times. If the longest follow-up time is censored, emean (extended mean) computes the mean survival by exponentially extending the survival curve to zero, and rmean (restricted mean) computes the mean survival time restricted to the longest follow-up time. If the longest follow-up time is a failure, the restricted mean survival time and the extended mean survival time are equal.

p(#) specifies the percentile of survival time to be computed. For example, p(25) will compute the 25th percentile of survival times, and p(75) will compute the 75th percentile of survival times. Specifying p(50) is the same as specifying the median option.

ccorr specifies that the standard error for the restricted mean survival time be computed using a continuity correction. ccorr is valid only with the rmean option.

noshow prevents stci from showing the key st variables. This option is seldom used because most people type stset, show or stset, noshow to set whether they want to see these variables mentioned at the top of the output of every st command; see [ST] stset.

dd(#) specifies the maximum number of decimal digits to be reported for standard errors and confidence intervals. This option affects only how values are reported and not how they are calculated.

level(#) specifies the confidence level, as a percentage, for confidence intervals. The default is level(95) or as set by set level.

graph specifies that the exponentially extended survivor function be plotted. This option is valid only when the emean option is also specified and is not valid in conjunction with the by() option.

tmax(#) is for use with the graph option. It specifies the maximum analysis time to be plotted.

+------+ ----+ Plot +-------------------------------------------------------------

cline_options affect the rendition of the plotted lines; see [G-3] cline_options.

+-----------+ ----+ Add plots +--------------------------------------------------------

addplot(plot) provides a way to add other plots to the generated graph; see [G-3] addplot_option.

+-----------------------------------------+ ----+ Y axis, X axis, Titles, Legend, Overall +--------------------------

twoway_options are any of the options documented in [G-3] twoway_options, excluding by(). These include options for titling the graph (see [G-3] title_options) and for saving the graph to disk (see [G-3] saving_option).

Examples with single-record survival data

Setup . webuse page2

Compute median survival time . stci

Compute median survival time by group . stci, by(group)

Compute the 25th percentile of survival time . stci, p(25)

Compute the 25th percentile of survival time by group . stci, p(25) by(group)

Compute mean survival time restricted to the longest follow-up time by group . stci, rmean by(group)

Compute mean survival time by exponentially extending the survival curve to 0 . stci, emean

Same as above, but also plot the exponentially extended survivor function . stci, emean graph

Examples with multiple-record survival data

Setup . webuse stan3

Compute median survival time . stci

Compute median survival time by group . stci, by(posttran)

Report whether values of posttran within subject vary over time . stvary posttran

Examples with multiple-failure data

Setup . webuse mfail2

Show st settings . stset

Compute median survival time . stci

Create nf containing the cumulative number of failures for each subject as of the entry time for the observation . stgen nf = nfailures()

Compute median survival time by group . stci, by(nf)

Stored results

stci stores the following in r():

Scalars r(N_sub) number of subjects r(p#) #th percentile r(rmean) restricted mean r(emean) extended mean r(se) standard error r(lb) lower bound of CI r(ub) upper bound of CI


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