Student's t test for unpaired or paired samples.
This file is applicable for equal or unequal sample sizes; for paired or
unpaired samples. When the test is unpaired, the Fisher-Snedecor F-test is
performed to assess the equality of variance. If variances are not equal,
Satterthwaite's approximate t test is performed.
Syntax: TESTT(X1,X2,TST,ALPHA,TAIL)

Inputs:
X1 and X2 - data vectors (mandatory).
TST - unpaired (0) or paired (1) test (default = 0).
ALPHA - significance level (default = 0.05).
TAIL - 1-tailed test (1) or 2-tailed test (2). (default = 1).
Outputs:
- t value.
- degrees of freedom.
- Confidence interval of means difference (for paired test)
- p-value
- Power
Example:
X1=[77 79 79 80 80 81 81 81 81 82 82 82 82 83 83 84 84 84 84 85 ...
85 86 86 87 87];

X2=[82 82 83 84 84 85 85 86 86 86 86 86 86 86 86 86 87 87 87 88 ...
88 88 89 90 90];

Calling on Matlab the function: testt

Answer is:

FISHER-SNEDECOR F-TEST FOR EQUALITY OF VARIANCES

F DF_numerator DF_denominator p_value
______ ____________ ______________ _______

1.5379 24 24 0.29861

--------------------------------------------------------------------------------
Variances are equal
--------------------------------------------------------------------------------

STUDENT'S T-TEST FOR UNPAIRED SAMPLES

t DF tail p_value Power
______ __ ____ _________ _______

5.2411 48 1 1.765e-06 0.99958

STATS=TESTT(...) returns a structure with all test(s) statistics

Created by Giuseppe Cardillo
giuseppe.cardillo-edta@poste.it

To cite this file, this would be an appropriate format:
Cardillo G. (2006). Student t-Test for unpaired or paired samples.
http://www.mathworks.com/matlabcentral/fileexchange/12699