Two different technicians Tech A and Tech B each measured th

Two different technicians (Tech A and Tech B) each measured the cardiac output for a sample of 36 patients using Doppler Echocardiaography. The supervisor would like to use this paired data to assess inter-rater reliability by testing if the population mean difference in cardiac output is 0 (no difference on average) versus the alternative that there is a difference. The hypotheses to be tested are: H0: d = 0 versus Ha: d 0, using a 10% significance level.

You remember some condition about a normal model required for the t test to be valid and want to check this condition. You recall that a QQ plot helps to assess if a population of responses can be considered normally distributed. How many QQ plots do you need to make in this case?

A. One QQ Plot of the sample of differences in measurements

B. One QQ Plot of the population of differences in measurements

C. Two QQ Plots, one for the sample of measurements by Tech A and one for the sample of measurements by Tech B

D. Two QQ Plots, one for the population of measurements by Tech A and one for the population of measurements by Tech B

Solution

Answer : A. One QQ Plot of the sample of differences in measurements