You are examining the return on equity ratios of the nation's commercial airlines. You have calculated the mean ROE to be 8%, and the sum of the squared ROEs is 0.27. Assuming there are 30 commercial airlines, what is the population standard deviation of ROEs in this industry?
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A. B. C. D.A
The population standard deviation is the positive square root of the population variance. The population variance is equal to the sum of the squared differences between each population member and the population mean, divided by the number of items in the population. There is, however, an equivalent alternate formula that is more often used for large amounts of calculation. It is equal to the average squared observation less the squared mean. In this case, we have the average squared observation will be 0.27 / 30 = 0.009, less the squared mean of 8%. We have 0.009 - 0.0064 = 0.0026 = 26%%. The square root of this number, 5.1%, will be the population standard deviation.