Degrees of Freedom For Example 1 on page 409, we used df = smaller of n1 - 1 and n2 - 1, we got df = 39, and the corresponding critical value is t = 1.685. If we calculate df using Formula 9-1, we get df = 76.423, and the corresponding critical value is t = 1.665.

How is using a critical value of t = 1.685 more “conservative” than using the critical value of t = 1.665? ( Hint: What magnitude of difference between the two sample means is required when using a critical value of t = 1.685 compared to the critical value of 1.665?)