heterogi

Stata help for heterogi

-------------------------------------------------------------------------------
help for heterogi
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Heterogeneity measures



    heterogi #Q #df [, level(#) format(%fmt) ncchi2 ]



    where



    #Q is the Cochran's Chi-Square or Q-test
    #df is the degrees of freedom



Description



    heterogi provides the statistics H and I^2 to quantify
          heterogeneity in a meta-analysis.



Remark



    It is an immediate command, see help immed. The Q-test can be
          obtained by metan or meta command.
 
Options



    level(#) specifies the width of the confidence interval; see help level.



    format(%fmt) specifies the display format for presenting numbers in the
        table's cells.



    ncchi2 specifies the use of the noncentral chi-squared distribution to
        calculate confidence intervals. The default is the test-based
        confidence interval (Higgins and Thompson, 2002).



Examples



     . heterogi 14.4 24
     . heterogi 14.4 24, level(99)
     . heterogi 14.1 11, nc
     . heterogi 81.5 19, nc f(%3.2f)
     . heterogi 41.5  7
     . heterogi 130.3 3



Authors



    Nicola Orsini, Division of Nutritional Epidemiology, IMM, Karolinska
    Institutet, Sweden
    Julian P.T. Higgins, MRC Biostatistics Unit, Cambridge, UK
    Matteo Bottai, Arnold School of Public Health, University of South
    Carolina, USA
    Iain Buchan, Northwest Institute for Bio-Health Informatics, University
    of Manchester, UK



Reference



    Higgins J.P.T. and Thompson S.G., Quantifying heterogeneity in a
    meta-analysis, Statistics in Medicine, 2002, 21: 1539-1558



Support



    http://nicolaorsini.altervista.org
    nicola.orsini@ki.se



Also see



On-line:  help for metan, meta (if installed)

Worked examples for heterogi

Click here to run or save the do-file

. capture net install http://nicolaorsini.altervista.org/stata/heterogi

. which heterogi
c:\ado\stbplus\h\heterogi.ado
*! version 2.0 N.Orsini, I. Buchan, 25 Jan 06
*! version 1.0 N.Orsini, J.Higgins, M.Bottai, 16 Feb 2005

. 
. heterogi 14.4 24

------------------------------------------------------
Statistic |       Estimate        [95% Conf. Interval]
----------+-------------------------------------------
        H |          1.0               1.0    1.3     
      I^2 |           0                  0    44      
------------------------------------------------------
Q-test = 14.4 d.f. = 24 p-value = 0.9371

. heterogi 14.4 24, level(99)

------------------------------------------------------
Statistic |       Estimate        [99% Conf. Interval]
----------+-------------------------------------------
        H |          1.0               1.0    1.5     
      I^2 |           0                  0    53      
------------------------------------------------------
Q-test = 14.4 d.f. = 24 p-value = 0.9371

. heterogi 14.1 11, nc

------------------------------------------------------
Statistic |       Estimate        [95% Conf. Interval]
----------+-------------------------------------------
        H |          1.1               1.0    1.6     
      I^2 |          22                  0    60      
------------------------------------------------------
Q-test = 14.1 d.f. = 11 p-value = 0.2275

. heterogi 81.5 19, nc f(%3.2f)

------------------------------------------------------
Statistic |       Estimate        [95% Conf. Interval]
----------+-------------------------------------------
        H |         2.07              1.64    2.49    
      I^2 |         76.69            62.79    83.81   
------------------------------------------------------
Q-test = 81.5 d.f. = 19 p-value = 0.0000

. heterogi 41.5  7

------------------------------------------------------
Statistic |       Estimate        [95% Conf. Interval]
----------+-------------------------------------------
        H |          2.4               1.8    3.3     
      I^2 |          83                 68    91      
------------------------------------------------------
Q-test = 41.5 d.f. = 7 p-value = 0.0000

. heterogi 130.3 3

------------------------------------------------------
Statistic |       Estimate        [95% Conf. Interval]
----------+-------------------------------------------
        H |          6.6               5.1    8.6     
      I^2 |          98                 96    99      
------------------------------------------------------
Q-test = 130.3 d.f. = 3 p-value = 0.0000