Question

An article reports measurements of the total power, on the log scale, of the heart rate variability, in the frequency range 0.003 to 0.4 Hz, for a group of 40 patients aged 25–49 years and for a group of 43 patients aged 50–75 years. The mean for the patients aged 25–49 years was 4 with a standard deviation of 0.23, and the mean for the patients aged 50–75 years was 3.4 with a standard deviation of 0.28. Let μX represent the population mean for the patients aged 25-49 years and let μY represent the population mean for the patients aged 50-75 years. Find a 95% confidence interval for the difference μX−μY. Round the answers to three decimal places.

The 95% confidence interval is ( , ).

Answer 1

Mean and standard deviation for Age group(25-49) years:    

Mean and standard deviation for Age group(50-75) years:    

Confidence interval is calculated using the formula:

where, pooled variance

Critical value:

Calculation for 95% confidence interval for

So, the 95% confidence interval for difference of population mean is