An article reports measurements of the total power, on the logscale, of the heart rate variability, in the frequency range 0.003to 0.4 Hz, for a group of 40 patients aged 25–49 years and for agroup of 43 patients aged 50–75 years. The mean for the patientsaged 25–49 years was 4 with a standard deviation of 0.23, and themean for the patients aged 50–75 years was 3.4 with a standarddeviation of 0.28. Let μX represent the population mean for thepatients aged 25-49 years and let μY represent the population meanfor the patients aged 50-75 years. Find a 95% confidence intervalfor the difference μX−μY. Round the answers to three decimalplaces.
The 95% confidence interval is ( , ).
