Stata: Data Analysis and Statistical Software

 gsum calculates summary statistics for an ordinal variable were each
    category represents a range of a conceptually continuous variable. gsum
    provides the weighted N, the mean, the standard deviation, and quantiles
    0.25, 0.50 (the median), and 0.75 (you can specify any set of quantiles you
    want).  Each quantile is available as both the midpoint of the category in
    which the quantile falls, or as a linear interpolation of that quantile
    based on methods presented by Blalock (1979).

    gsum can also produce a value table (which can also be saved) listing each
    category, the range, the midpoint of that range, the number of cases, the
    weight of each case, and the cumulative distribution function (CDF).

    For an extra tool, gsum can also create a new variable that contains the
    midpoints.

    gsum accepts any type of [weight] and is byable.

    For example, you may have a variable age_cat where 1 represents 18-24 years
    of age, 2 represents 25-44 years of age, and 3 represents 45-100 years of
    age.  You can use gsum to calculate summary statistics such as the mean,
    median, and standard deviation.

-Eric




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