# TEST MeanDifference

Document Sample

```					Spreadsheet for Computing the Statistical Significance (p-value) of the
Difference in Two Means, Two Different Groups
- by Brian Stipak

Input:

Group 1         Group 2
N=
mean =
std dev =

Results:
2-tail P-value:   #DIV/0!
1-tail P-value:   #DIV/0!

Instructions:
Input the number of cases (N), the sample mean, and the sample standard
deviation for each of the two groups in the six cells of the input section above.

Warning:
The calculated p-values above become inaccurate for df less than 5, so do not
use if df<5:           df = #DIV/0!
-value) of the

ple standard
put section above.

than 5, so do not
STATISTICS:

DIFF =      0            |t| = #DIV/0!
SIGMA = #DIV/0!            df = #DIV/0!

P-value is estimated by converting the t-statistic to an approximate Z,
and then calculating p-value for Z (See Lotus, Vol 3, July 1987, p. 52).

t-statistic converted to Z =    #DIV/0!

NORMAL DISTRIBUTION CALCULATIONS FOR DETERMINING 2-TAIL P-VALUE:

Constants                      Intermediate Calculations

a           0.04987                              1             Note: Z in
b           0.02114            aZ          #DIV/0!             calculations
c           0.00328            b(Z^2)      #DIV/0!             is absolute value
d           3.8E-05            c(Z^3)      #DIV/0!             of Z.
e           4.9E-05            d(Z^4)      #DIV/0!
f           5.4E-06            e(Z^5)      #DIV/0!             For explanation
f(z^6)      #DIV/0!             of these calcula-
-----            tions see Lotus,
sum         #DIV/0!             Vol 5, No 12
(Dec 1989), p. 59.
2-tail P-value:       =====>    #DIV/0! <=====

NOTE:
Using current versions of Excel that have the Normdist function, you can use that function to compute the P-value, r
2-tail P-value:     =====> #DIV/0! <=====
o compute the P-value, rather than using the above calculations:

```
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
 views: 9 posted: 10/14/2012 language: English pages: 4
How are you planning on using Docstoc?