How to get the p value? What is the formula? And how to know if one tailed or two tailed?

Use the formula: 1 = Where d = sample mean difference n = number of sample mean differences Sd = standard deviation of the sample differences Using the formula above, it will give us t = 13.57/(8.017V7) t = 4.478 Considering the data above, it will give us a p value of 0.004200 making our result significant at 0.05% level which means that the medication applied in the experiment has an effect on the test subjects