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Interpretation, difficulty 2 of 3

The sample mean missed

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An airline's booking system holds the weight of every checked bag on a route last year — the whole population. Their mean is $\mu = 18.6$ kg, and individual bags typically differ from that mean by about 4 kg (some weigh 10 kg, some 27 kg). For a training exercise, a trainee draws a random sample of 40 of last year's bag records and finds $\bar{x} = 19.3$ kg. What is the best conclusion?