Exercise 1: A One-Sample t-test, n=16 — Possible Solution ==================================================================== GIVEN ------------------------------ H0: mu = 50 n = 16, x-bar = 54, s = 10 STEP 1: THE STANDARD ERROR ------------------------------ SE = s / sqrt(n) = 10 / sqrt(16) = 10 / 4 = 2.5 STEP 2: THE T-STATISTIC ------------------------------ t = (x-bar - mu0) / SE = (54 - 50) / 2.5 = 4 / 2.5 = 1.6 STEP 3: DEGREES OF FREEDOM ------------------------------ df = n - 1 = 16 - 1 = 15 STEP 4: THE DECISION ------------------------------ Given critical value at two-tailed alpha=0.05, df=15: 2.131 |t| = 1.6, which is less than 2.131. Per this chapter's own decision rule, we FAIL TO REJECT H0 - the observed sample mean is not far enough from 50 (in units of standard error, accounting for the extra t-distribution uncertainty from estimating s) to conclude a real difference exists. WHY THIS WORKS AS AN ANSWER ------------------------------ Each quantity is computed in the sequence this chapter's own one- sample t-test method uses - standard error using the sample s, then the t-statistic, then degrees of freedom via n-1 - and the decision is made by directly comparing the resulting |t| against the given critical value.