A loan officer compares the interest rates for 48-month fixed-rate auto loans and 48-month variable-rate auto loans. Two independent, random samples of auto loan rates are selected. A sample of five 48-month variable-rate auto loans had the following loan rates: 3.01% 2.882% 3.23% 2.40% 3.23% while a sample of five 48-month fixed-rate auto loans had loan rates as follows: 4.040% 3.78% 4.375% 3.71% 4.21% Figure 11.7 OMP Output of Testing the Equality of Mean Loan Rates for Variable and Fixed 48-Month Auto Loans Means and Std Deviations Level Fixed Variable Number 5 5 Mean 4.02300 2.95040 Std Dev 0.341878 8.281149 t Test Variable-Fixed Assuming equal variances Difference Std Err Dif -1.0726 t Ratio -5.41847 0.1980 DF B Upper CL Dif -0.6161 Probit 0.0006 Lower CL Dif Confidence -1.5291 Prob > t 0.9997 8.95 Prob t