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.

Definition Definition Measure of central tendency that is the average of a given data set. The mean value is evaluated as the quotient of the sum of all observations by the sample size. The mean, in contrast to a median, is affected by extreme values. Very large or very small values can distract the mean from the center of the data. Arithmetic mean: The most common type of mean is the arithmetic mean. It is evaluated using the formula: μ = 1 N ∑ i = 1 N x i Other types of means are the geometric mean, logarithmic mean, and harmonic mean. Geometric mean: The nth root of the product of n observations from a data set is defined as the geometric mean of the set: G = x 1 x 2 ... x n n Logarithmic mean: The difference of the natural logarithms of the two numbers, divided by the difference between the numbers is the logarithmic mean of the two numbers. The logarithmic mean is used particularly in heat transfer and mass transfer. ln x 2 − ln x 1 x 2 − x 1 Harmonic mean: The inverse of the arithmetic mean of the inverses of all the numbers in a data set is the harmonic mean of the data. 1 1 x 1 + 1 x 2 + ...