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help for ^meta^                                            (STB-38: sbe16)
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Fixed and random-effects meta-analysis, with graphics
-----------------------------------------------------

^meta^ ^theta setheta^ [^if^ exp] [^in^ range], [^ef^orm ^pr^int ^eb^ayes ^l^evel^(^#^)^
      ^gr^aph^(f^|^r^|^e)^ ^id(^strvar^)^ ^fm^ult^(^#^)^ ^boxy^sca^(^#^)^ ^boxsh^ad^(^#^)^ ^cl^ine
      ^ltr^unc^(^#^)^ ^rtr^unc^(^#^)^]


Description
-----------

^meta^ provides pooled estimates, confidence limits, and a test that the true
pooled effect is zero, obtained from fixed and random effects meta-analysis, a
test for heterogeneity between studies and an estimator of between studies
variance, and, optionally, plots the individual and pooled estimates.

^theta^ is the effect estimate from the individual study, and ^setheta^ is
its standard error. For example theta might be a difference in means, a 
log rate ratio, a log odds ratio or a log hazard ratio.

If you have a dataset which contains data for all studies, then the @byvar@
command can be used to derive the effect estimates and standard errors for the
individual studies. For example:

. ^sort study^
. ^byvar study, coef(group) se(group) generate:^
. ^quietly poisson cases group, e(pyrs)^
. ^sort study^
. ^qui by study: keep if _n==1^
. ^rename _C_1 logrr^
. ^rename _S_1 se^
. ^meta logrr se^

Alternatively, the @collapse@ or @for@ commands may be useful.


Options
-------

^eform^ requests that the output is exponentiated. This is useful for effect
measures such as log odds ratios which are derived from generalized linear
models. If the ^eform^ and ^graph^ options are used, then the graph output is 
exponentiated, with a log scale for the x axis.  If either the ^print^ or
the ^ebayes^ option are used together with the ^eform^ option, the resulting
empirical Bayes estimates are exponentiated.

^print^ requests that additionally, the weights used in the fixed and random
effects estimation are listed for each study, together with the individual
study estimates and confidence intervals.  The studies are labelled by name if
the ^id^ option is specified, or by number otherwise.  If the ^ebayes^ option
is specified, the study estimates and confidence intervals are empirical
Bayes.

^ebayes^ creates two new variables in the dataset: ^ebest^ contains empirical
Bayes estimate for each study, and ^ebse^ the corresponding standard errors.
Any existing variables called ^ebest^ or ^ebse^ are overwritten.

^level(^#^)^ specifies the level for the confidence intervals (default 95).


Options for graphing results
----------------------------

^graph(f^|^r^|^e)^ requests a graph. The options ^graph(f)^ or ^graph(r)^
request that the combined estimate in the graph is derived using fixed or
random effects meta-analysis. The option ^graph(e)^ requests that empirical
Bayes estimates of the individual study estimates be plotted. In this case,
the combined estimate is the random-effects estimate, and the ^print^ and
^ebayes^ options are also automatically requested.

Graph options are allowed, except for ^ylabel()^, ^symbol()^, ^xlog^, ^ytick^
and ^gap^.

^id(^strvar^)^ is a character variable which is used to label the studies.  If
the data contains a labelled numeric variable then the @encode@ command can be
used to create a character variable

^fmult(^#^)^ is a number greater than zero which can be used to scale 
the font size for the study labels. The font size is automatically
reduced if the maximum label length is greater than 8, or the number
of studies is greater than 20. However it may be possible to increase
it somewhat over the default size.

^boxysca(^#^)^ provides a number ^#^ between zero and 1 which can be used to
reduce the vertical length of the boxes. This is used to make boxes square if
a vertical magnification of more than 100 has been used to increase the length
of the graph. The default is 1.

^boxshad(^#^)^ provides an integer ^#^ between 0 and 4 which gives the box shading
(0 most, 4 no shading). The default is 0.

^cline^ asks that a vertical dotted line be drawn at the combined estimate.

^ltrunc(^#^)^ truncates the left side of the graph at ^#^. This is used to truncate
very wide confidence intervals. However ^#^ must be less than each of the
individual study estimates.

^rtrunc(^#^)^ truncates the right side of the graph at ^#^, and must be greater than
each of the individual study estimates.


Authors
-------

       Stephen Sharp
       London School of Hygiene and Tropical Medicine, UK
       email: stephen.sharp@@lshtm.ac.uk

       Jonathan Sterne
       United Medical and Dental Schools, UK
       email: j.sterne@@umds.ac.uk


Also see
--------

    STB: sbe16 (STB-38)
On-line: help for @byvar@, @collapse@, @for@.