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help for ^adjmean^ (STB-43: sg33.1)
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Adjusted means (JMGarrett 02/04/98)
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^adjmean^ yvar [^if^ exp]^, by(^xvar1 [xvar2]^)^ [^a^djust^(^covlist^) m^odel
^l^evel^(^#^) g^raph ^b^ar graph_options]
^adjmean^ calculates and optionally graphs adjusted means and confidence
intervals from linear regression estimates for one or two nominal X
variables, adjusted for covariates. If a second X is specified, means
are calculated for all possible combinations of X categories, and an
interaction effect is tested. Default shows estimated means and confidence
intervals only. Optionally, model estimates and/or a graph may be displayed.
Dummy variables are created for xvar1. The lowest dummy variable defaults
to the reference group. If xvar2 is specified, dummy variables are created
for it also, as well as interaction terms.
Variables and options required
------------------------------
yvar -- dependent variable (continuous)
^by(^xvar1^)^ -- nominal variable for categories of estimated means
^by(^xvar1 xvar2^)^ -- categories of all combinations of xvar1 and
xvar2; interaction between xvar1 and xvar2 tested
Options allowed
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^adjust(^covlist^)^ -- any covariates (if none specified, unadjusted means
reported); Covariates are set to their mean, based on
observations used in the analysis, or can be set to user
specified values (e.g., age=50 gender=1).
^model^ -- shows linear regression table as well as estimated means
^level(^#^)^ -- specifies the confidence level, in percent, for calculation
of confidence intervals of the adjusted means (default=95%)
^graph^ -- if one X (xvar1), graphs means and confidence intervals; if
both xvar1 and xvar2 specified, points graphed for each mean, but
confidence intervals are not graphed; xvar1 is used for the x-axis
with separate points for categories of xvar2
^bar^ -- can be used with the ^graph^ option to display a bar graph instead
of points
Examples
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. ^adjmean chol, by(race) adjust(sys age=50)^
Calculates the mean cholesterol level by race category,
adjusted for mean systolic blood pressure and age=50
. ^adjmean chol, by(ses) adjust(sys age) model graph xlabel(1,2,3) ylabel^
Calculates the mean cholesterol by levels of socio-economic status,
adjusted for systolic blood pressure and age; displays model and graph
. ^adjmean sbp, by(gender race) adjust(age smoke etoh) level(90) ^
Calculates the mean cholesterol for all combinations of gender
(2 categories) and race (4 categories) for a total of 8 means, adjusted
for age, smoking status, and alcohol consumption; tests for interaction
between gender and race; 90% confidence intervals
. ^adjmean sbp, by(race gender) adjust(age smoke etoh) graph bar ylabel^
Calculates adjusted mean cholesterol for all combinations of gender
and race; bar graph of means, race on the x-axis
Author
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Joanne M. Garrett
University of North Carolina at Chapel Hill
garrettj@@med.unc.edu
See also
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STB: STB-43 sg33.1, STB-24 sg33