Warfarin is a drug used to prevent blood clots, for example in patients with irregular heartbeat and after heart surgery. However, too much warfarin can cause unusual bleeding or bruising, so calibration of the dose is important. A study contrasting calibration times (in hours) in two ethnic groups had the following results. For the sample of 19 Caucasians, the times were 2, 4, 6, 7, 8, 9, 10, 10, 12, 14, 16, 19, 21, 24, 26, 30, 35, 44, and 70; for the 18 Asian–Americans, the times were 2, 2, 3, 3, 4, 5, 5, 6, 6, 6, 7, 7, 8, 9, 10, 12, 19, and 32.
(1) Display the data numerically to compare the two ethnic groups.
(2) Display the data graphically to compare the two ethnic groups.
(3) Describe the distribution of the data within ethnic group.
(4) Log transform the data and repeat the graphical display. How do the displays with and without log transformation compare?
(5) Can you think of other variables you might want to adjust to help understand the ethnic differences better?