Tests of Differences between Means, Independent Groups, Standard Deviation Estimated (2 of 8)

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2. The second step is to choose a significance level. Assume the .05 level is chosen.
   
3. The third step is to compute the difference between sample means (M_d). In this example, M_t = 63.89, M_N = 46.79 and M_d = MT - M_N = 17.10.
   
   
4. The fourth step is to compute p, the probability (or probability value) of obtaining a difference between and the value specified by the null hypothesis (0) as large or larger than the difference obtained in the experiment. Applying the general formula,
   
   
   
   where M_d is the difference between sample means, µ₁ - µ₂ is the difference between population means specified by the null hypothesis (usually zero), and is the estimated standard error of the difference between means.