Independent Samples t-Test - Comparing Two Means with Equal Variances

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The test statistic is:

t = \frac{\bar{x} - \bar{y}}{s \sqrt{\frac{1}{m} + \frac{1}{m}}}


\bar{x} and \bar{x} are the average values of variables x and y respectively, where each of these variables represents the data from two independent groups,
the groups have sample sizes of m and n respectively,
s = \sqrt{d_{eff}\frac{(m-1)s^2_x + (m-1)s^2_y }{m + n - 2b}},
b is 1 if Bessel's correction for Means is selected in Statistical Assumptions and 0 otherwise,
s^2_x and s^2_y are the sample variances in the two groups,
d_{eff} is Extra Deff.
 p = 2\Pr(t_{n+m-2} \ge |t|)