A company is interested in comparing the mean sales revenue per salesperson at two different locations. The manager takes a random sample of 10 salespeople from each location independently and records the sales revenue generated by each person during the last four weeks. He decides to use a t-test to compare the mean sales revenue at the two locations.

Which of the following assumptions is necessary for the validity of the t-test?*

-The population standard deviations at both locations are equal.

-The population standard deviations at both locations are known.

-The population of the sales records at each location is normally distributed.

-The population standard deviations at both locations are not equal.

-The population of the difference in sales records computed by pairing one salesperson from each location is normally distributed.

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