In given Problem, use the standard deviations for bleeding times calculated from 43 bleeding times without pressure and from 39 bleeding times under pressure to decide whether bleeding time under pressure is more variable than bleeding time without pressure
Problem
To study whether or not pressure exerted on the upper arm increases bleeding time, 39 persons had their upper arm subjected to a pressure of 40 mmHg of mercury and their fingers pricked. Their mean bleeding time was 2.192 min, and the standard deviation of their bleeding times was .765 min. Forty-three other persons acted as controls. No pressure was used for the controls, and their bleeding time was found to have a mean of 1.524 minutes and a standard deviation of .614min. Give a 95% confidence interval for the difference in bleeding times. Do you think pressure increases mean bleeding time? Why?