A Coffee Shop Franchise Owner Is Looking at Two Possible $\sigma$

question 37

Essay

A coffee shop franchise owner is looking at two possible locations for a new shop.To help make a decision the owner looks at the number of pedestrians that go by each of the two locations in one-hour segments.At location A,counts are taken for 35 one-hour units and with a mean number of pedestrians of 421 and a sample standard deviation of 122.At the second location (B),counts are taken for 50 one hour units with a mean number of pedestrians of 347 and a sample standard deviation of 85.Assume the two populations variances are not known but are equal,and that the number of pedestrians is approximately normal.
-Calculate the pooled estimate of $\sigma$
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