CLASS NO: A medical researcher wants to compare the pulse rates of smokers and non-smokers. He believes that the pulse rate for smokers is larger than non-smokers. To test his claim, he selects a random sample of 20 smokers and found that their mean pulse rate is 76, and he also selects another sample of 20 non-smokers randomly and found that their mean pulse rate is 72. Based on past experience, the standard deviation of the pulse rates is known to be 9 for smokers and 10 for non-smokers. Test the researcher's claim at 6% level of significance. (?? marks)