Question

to test the effectiveness of a new treatment, a clinician measures cholesterol levels (in mg/dl) of 9 patients before and after treatment. the mean difference is 12, and the standard deviation of the differences is 6. what is the degrees of freedom (df) for this test? 6 7 8 9

Explanation:

Step1: Recall the formula for degrees of freedom in paired - t test

For a paired - t test, the degrees of freedom formula is \(df=n - 1\), where \(n\) is the number of pairs.

Step2: Identify the value of \(n\)

Here, the number of patients (pairs) \(n = 9\).

Step3: Calculate the degrees of freedom

Substitute \(n = 9\) into the formula \(df=n - 1\). So, \(df=9 - 1=8\).

Answer:

8