Tests of Pearson's Correlation (2 of 6)

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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 (zero) as large or larger than the difference obtained in the experiment. This can be calculated using the following formula:
   
   
   
   
   The degrees of freedom are N-2 where N is the sample size.
   
   
   For this example,
   
   
   
   The df are N - 2 = 100 - 2 = 98. A t table can be used to find that the two-tailed probability value for a t of 2.776 with 98 df is 0.007.