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help for allsubsets
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All subsets (combinatorial) meta-analysis

    allsubsets varlist [if expression] [in range], save(filename)
                 [maxstudies(integer) replace ]

Description

    allsubsets performs all subsets (combinatorial) meta-analysis in a set of
        studies and saves results.  By default the routine performs fixed
        effects meta-analysis using the inverse variance method, and random
        effects meta-analysis using the DerSimonian and Laird random effects
        model.

Let N be the number of studies in the meta-analysis.
Then the number of possible subsets is -1+2^N. 
The command handles up to N=maxstudies studies. See Options. 

Suggested citation:

    Olkin I, Dahabreh IJ, Trikalinos TA. GOSH - A graphical display of study
        heterogeneity. Research Synthesis Methods. 2012;3(3):214-223.

See also the Center for Evidence-based Medicine (CEBM) at Brown University for 
> updates or additional materials.

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    varlist Expects two numeric variables: the effect size Theta and its
        variance var_theta.

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    In the saved file one finds the following variables:

    study_ES: the effect size of the study. has non-missing values only for N
        (# of studies) observations.

    study_var: the variance of each study. has non-missing values only for N
        (# of studies) observations.

    es_fem: fixed effects meta-analysis result

    es_rem: random effects meta-analysis result

    df: degrees of freedom

    I2: I^2 value

    subset: codes which studies are in the subset.  Studies are named with
        lowercase letters (e.g. "a", "b"). "a b g" means that the 2nd, 3rd
        and 7th study are included in the subset.

    pRem_z: p-value for the overall effect with the random effects model

    var_fem: variance of the summary fixed effects estimate

    var_rem: variance of the summary random effects estimate

    Q: Cochran's Q

    tau2: DerSimonian and Laird 1-step tau^2

    pFem_z: p-value for the overall effect with fixed effects



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    Options for allsubsets


    save Give the nane of the file where the command will save results

    replace Whether or not to replace the file if it exists.

    maxstudies The maximum number of studies that are allowed. This depends
        on your computer's RAM. The default is N=20 (1'048'575 subsets).
        Specifying too high an N results in a memory allocation error.