Stata 15 help for tabodds

[R] epitab -- Tables for epidemiologists (tabodds)

Syntax

tabodds var_case [expvar] [if] [in] [weight] [, tabodds_options]

tabodds_options Description ------------------------------------------------------------------------- Main binomial(varname) number of subjects variable level(#) set confidence level; default is level(95) or report odds ratio adjust(varlist) report odds ratios adjusted for the variables in varlist base(#) reference group of control variable for odds ratio cornfield use Cornfield approximation to calculate CI of the odds ratio woolf use Woolf approximation to calculate SE and CI of the odds ratio graph graph odds against categories ciplot same as graph option, except include confidence intervals

CI plot ciopts(rcap_options) affect rendition of the confidence bands

Plot marker_options change look of markers (color, size, etc.) marker_label_options add marker labels; change look or position cline_options affect rendition of the plotted points

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 ------------------------------------------------------------------------- fweights are allowed; see weight.

Menu

Statistics > Epidemiology and related > Tables for epidemiologists > Tabulate odds of failure by category

Description

tabodds is used with case-control and cross-sectional data. It tabulates the odds of failure against a categorical explanatory variable expvar. If expvar is specified, tabodds performs an approximate chi-squared test of homogeneity of odds and a test for linear trend of the log odds against the numerical code used for the categories of expvar. Both tests are based on the score statistic and its variance; see Methods and formulas. When expvar is absent, the overall odds are reported. The variable var_case is coded 0/1 for individual and simple frequency records and equals the number of cases for binomial frequency records.

Optionally, tabodds tabulates adjusted or unadjusted odds ratios, using either the lowest levels of expvar or a user-defined level as the reference group. If adjust(varlist) is specified, it produces odds ratios adjusted for the variables in varlist along with a (score) test for trend.

Options

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

binomial(varname) supplies the number of subjects (cases plus controls) for binomial frequency records. For individual and simple frequency records, this option is not used.

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

or specifies that odds ratios be produced; see base() for details about selecting a reference category. By default, tabodds will calculate odds.

adjust(varlist) specifies that odds ratios adjusted for the variables in varlist be calculated.

base(#) specifies that the #th category of expvar be used as the reference group for calculating odds ratios. If base() is not specified, the first category, corresponding to the minimum value of expvar, is used as the reference group.

cornfield requests that the Cornfield (1956) approximation be used to calculate the confidence interval of the odds ratio. By default, tabodds reports a standard-error-based interval, with the standard error coming from the square root of the variance of the score statistic.

woolf requests that the Woolf (1955) approximation, also known as the Taylor expansion, be used for calculating the standard error and confidence interval for the odds ratio. By default, tabodds reports a standard-error-based interval, with the standard error coming from the square root of the variance of the score statistic.

graph produces a graph of the odds against the numerical code used for the categories of expvar. All graph options except connect() are allowed. This option is not allowed with either the or option or the adjust() option.

ciplot produces the same plot as the graph option, except that it also includes the confidence intervals. This option may not be used with either the or option or the adjust() option.

+---------+ ----+ CI plot +----------------------------------------------------------

ciopts(rcap_options) is allowed only with the ciplot option. It affects the rendition of the confidence bands; see [G-3] rcap_options.

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

marker_options affect the rendition of markers drawn at the plotted points, including their shape, size, color, and outline; see [G-3] marker_options.

marker_label_options specify if and how the markers are to be labeled; see [G-3] marker_label_options.

cline_options affect whether lines connect the plotted points and the rendition of those 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

Setup . webuse bdesop

Tabulate the odds of cancer against alcohol consumption . tabodds case alcohol [fw=freq]

Same as above, but report odds ratios rather than odds . tabodds case alcohol [fw=freq], or

Tabulate Mantel-Haenszel age-adjusted odds ratios . tabodds case alcohol [fw=freq], adjust(age)

Same as above, but adjust for tobacco use instead of age . tabodds case alcohol [fw=freq], adjust(tobacco)

Stored results

tabodds stores the following in r():

Scalars r(odds) odds r(lb_odds) lower bound for odds r(ub_odds) upper bound for odds r(chi2_hom) chi-squared test of homogeneity r(p_hom) p-value for test of homogeneity r(df_hom) degrees of freedom for chi-squared test of homogeneity r(chi2_tr) chi-squared for score test for trend r(p_trend) p-value for score test for trend

References

Cornfield, J. 1956. A statistical problem arising from retrospective studies. In Vol. 4 of Proceedings of the Third Berkeley Symposium, ed. J. Neyman, 135-148. Berkeley, CA: University of California Press.

Woolf, B. 1955. On estimating the relation between blood group disease. Annals of Human Genetics 19: 251-253. Reprinted in Evolution of Epidemiologic Ideas: Annotated Readings on Concepts and Methods, ed. S. Greenland, pp. 108-110. Newton Lower Falls, MA: Epidemiology Resources.


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