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help for ^metap^                                 (STB-49: sbe28; STB-56: sbe28.1)
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Meta-analysis of p-values
-------------------------

	^metap^ pvar [^if^ exp] [^in^ range] [^, ^m^ethod^(^#^)^]


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

^metap^ provides combination of p-values from each study. The user provides the 
one-tail p-values as ^pvar^. 

If you have a dataset which contains data for all studies, then the @byvar@
command (STB-27) can be used to derive the p-values 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^
   . ^generate pvar=norprob(-logrr/se)^
   . ^metap p^

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


Options
-------

^method(^#^)^ combines the p-values three using different available: 

^f^: Fisher's method to combine pvalues. 
^ea^: Edgington's additive method based on the sum of probabilities (Edgington
    1972a), this method is suggested to combine a small number of studies, 
    producing similar results as Fisher's method. 
^en^: Edgington's normal curve method, based on the contrast of the p-value 
    average (Edgington 1972b), this method is suggested to combine a large 
    number of studies. By default Fisher's method is used.


References
----------

Edgington, E.S. (1972a). An additive method for combining probability values 
from independent experiments. Journal of Psychology, 80; 351-363.

Edgington, E.S. (1972b). A normal curve method for combining probability values
from independent experiments. Journal of Psychology, 82; 85-89.

Fisher, R.A. (1932). Statistical Methods for Research Workers (4th ed.) London:
Oliver&Boyd.


Examples
--------

   . ^metap pvar^
   . ^metap pvar, method(ea)^
   . ^metap pvar, method(en)^


Author
------

       Aurelio Tobias
       Universidad Miguel Hernandez, Alicante, Spain
       email: bledatobias@@ctv.es


Also see
--------

On-line:  help for @graph@, @byvar@, @collapse@, @for@, @meta@ (if installed), 
@metareg@ (if installed), @metabias@ (if installed), @metacum@ (if installed), 
@galbr@ (if installed), @metainf@ (if installed)