ODDSRATIOS Subcommand (CSLOGISTIC command)

The ODDSRATIOS subcommand estimates odds ratios for the specified factors or covariates. Note that these odds ratios are model-based and are not directly computed by using the observed data.

A separate set of odds ratios is computed for each category of the dependent variable (except the reference category).

If the FACTOR keyword is specified, the odds ratios compare the odds at each category j with the odds at category J, where J is the reference category defined in parentheses following the variable name of the factor. All other factors and covariates are fixed as defined on the CONTROL keyword.

If the COVARIATE keyword is specified, the odds ratios compare the odds at value x with the odds at value x + Δx, where Δx is the change in x defined in parentheses following the variable name of the covariate. To define the value x, specify the covariate and the value on the CONTROL keyword. All other factors and covariates are fixed as defined on the CONTROL keyword.

If a specified factor or covariate interacts with other predictors in the model, the odds ratios depend not only on the change in the specified variable but also on the values of the variables with which it interacts. If a specified covariate interacts with itself in the model (for example, X*X), the odds ratios depend on both the change in the covariate and the value of the covariate. The values of interacting factors and covariates can be customized by using the CONTROL keyword.

The CSLOGISTIC procedure sorts levels of each factor in ascending order and defines the highest level as the last level. (If the factor is a string variable, the value of the highest level is locale-dependent.)

  • Multiple ODDSRATIOS subcommands are allowed. Each subcommand is treated independently.
  • Either the FACTOR keyword and one or more factors, or the COVARIATE keyword and one or more covariates, but not both, are required. All other keywords are optional.
  • The FACTOR, COVARIATE, and CONTROL keywords must be followed by an equals sign and one or more elements enclosed in square brackets.
  • If a variable is specified on the FACTOR or COVARIATE keyword and is also specified on the CONTROL keyword, the CONTROL specification for that variable is ignored when the variable’s odds ratios are computed. Thus, FACTOR = [A B] CONTROL = [A(1) B(2)] estimates odds ratios for factor A holding factor B at level 2 and for factor B holding factor A at level 1.

FACTOR = [option]. Valid options are one or more factors appearing on the factor list. Optionally, each factor may be followed by parentheses containing the level to use as the reference category when computing odds ratios. Keyword LOW or HIGH, or a value, may be specified. Put the value inside a pair of quotes if the value is formatted (such as date or currency) or if the factor is of string type. By default, the highest category is used as the reference category.

  • If a value is specified but the value does not exist in the data, a warning is issued and the default HIGH is used.
  • Any factor may occur only once on the FACTOR keyword.

COVARIATE = [option]. Valid options are one or more covariates appearing on the covariate list. Optionally, each covariate may be followed by parentheses containing one or more nonzero numbers giving units of change to use for covariates when computing odds ratios. Odds ratios are estimated for each distinct value. The default value is 1. Any covariate may occur only once on the COVARIATE keyword.

CONTROL= [option]. Specifies the factor and/or covariate values to use when computing odds ratios. Factors must appear on the factor list, and covariates must appear on the covariate list, of the CSLOGISTIC command.

  • Factors must be followed by the keyword LOW or HIGH, or a value, in parentheses. Put the value inside a pair of quotation marks if the value is formatted (such as date or currency) or if the factor is of string type. If keyword LOW or HIGH is used, each odds ratio is computed by holding the factor at its lowest or highest level, respectively. If a value is used, each odds ratio is computed by holding the specified factor at the supplied value. If a factor is not specified on the CONTROL option, its highest category is used in odds ratio calculations.
  • If a factor value is specified but the value does not exist in the data, a warning is issued and the default HIGH is used.
  • Covariates must be followed by the keyword MEAN or a number in parentheses. If the keyword MEAN is used, each odds ratio is computed by holding the covariate at its overall mean. If a number is used, each odds ratio is computed by holding the specified covariate at the supplied value. If a covariate is not specified on the CONTROL option, its overall mean is used in odds ratio calculations.
  • Any factor or covariate may occur only once on the CONTROL keyword.