Degrees of freedom is a parameter used to help select the critical value in some probability distributions such as a T-test, F-test, Analysis of Variance (ANOVA), chi-square, etc. Degrees of freedom is the number of paired comparisons necessary to attain a critical value. For example, if you were asked how many paired comparisons would be needed to determine which of four straws is the longest, you would need three (3) paired comparisons. In test one, you would compare straw 1 with straw 2. The longer of those two straws would be compared with straw 3. The longer of those two straws with then be compared with straw 4. How many tests did we have to run? We had to run three tests to compare the four straws.