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| This method is called Stouffer's method and can be computed using this [attachment:combineZ.xls spreadsheet]. | This method is called Stouffer's method and may be computed using this [attachment:combineZ.xls spreadsheet]. |
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| Mosteller and Bush(1954) and Rosenthal (1987) also show how t statistics (each with degrees of freedom over 2) may be summed to obtain a combined t value. These computations are performed using this [attachment:combineT.xls spreadsheet]. | Mosteller and Bush(1954) and Rosenthal (1987) also show how t statistics (each with degrees of freedom over 2) may be summed to obtain a combined t value. These computations may be performed using this [attachment:combineT.xls spreadsheet]. |
Combining z values and t values with large numbers of degrees of freedom
Following Winer (1971) and Rosenthal (1987) the sum of z values divided by the square root of the number of terms being summed follows a Normal distribution. This method is called Stouffer's method and may be computed using this [attachment:combineZ.xls spreadsheet].
Mosteller and Bush(1954) and Rosenthal (1987) also show how t statistics (each with degrees of freedom over 2) may be summed to obtain a combined t value. These computations may be performed using this [attachment:combineT.xls spreadsheet].
References
Mosteller F, Bush RR (1954). Selected quantitative techniques. In: Lindzey G, ed. Handbook of Social Psychology, Cambridge, Mass: Addison-Wesley, pp 289-334.
Rosenthal R (1987) Judgement studies design analysis and meta-analysis. CUP:Cambridge.
Winer, B.J. (1971). Statistical principles in experimental design (2nd ed.). New York: McGraw-Hill. (1991 edition available in CBU library)