For questions 1 and 2 classify each bold faced number (there are two such number

Question

For questions 1 and 2 classify each bold faced number (there are two such numbers in each problem) as a parameter or statistic. The receiving department of a company inspects a truckload of ball bearings to determine whether the bearings are within specified size limits. It is known, by the shipper but not by the receiving department, that the average diameter of the bearings in this truck- load is 2.50cm. The receiving department obtains a random sample of 100 ball bearings from this truckload and finds that the average diameter of these bearings is 2.55cm. A telephone sales outfit in Los Angeles uses a device that dials residential phone numbers in the city at random. Of the first 200 numbers dialed, 47% are unlisted numbers. This is not surprising since 52% of all Los Angeles residential phone numbers are unlisted.

Explanation / Answer

Statistic describe a sample, whereas parameter describe a population. Therefore, in problem 1, 2.50 is population, as it refer to average diameter of bearing in truckload of all ball bearings. On the other hand, 2.55 refer to statistic, as the average diameter of these bearings have been computed from 100 random samples of ball bearings.

In problem 2, 47% refer to statistic, as this percentage of unlisted numbers have been found from first 200 number dialled by a telephone sales outfit in Los Angles. On the other hand, 52% refer to population percentage as this is the percentag eof unlisted phone numbers in Los Angles as a whole.

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