20. The term degree of freedom is used with reference to: A) Test of goodness of fit only B) Z-test and test of goodness of fit C) T-test and test of goodness of fit D) T-test and Z-test

The concept of degrees of freedom is crucial in statistics as it affects various hypothesis tests and distributions. For instance, in a t-test, the degrees of freedom (df) are computed based on the sample size, specifically df = n - 1, where n is the number of data points. This represents the number of values that are free to vary in a statistical calculation, highlighting the limitations imposed by fixed constraints. In real-world applications, degrees of freedom come into play in various statistical models. For example, when analyzing data for a clinical trial, degrees of freedom help researchers determine the validity of their t-tests or ANOVA results, aiding in making conclusions about the effectiveness of a new drug. Understanding how to calculate and interpret degrees of freedom can be the difference between meaningful insights and misleading results.