端同学2020-11-03 14:03:14

这题是怎么做出来的 In a metal fabrication process, metal rods are produced that have an average length of 20.5 metres with a standard deviation of 2.3 metres. A quality control specialist collects a random sample of 30 rods and measures their lengths. 问题Suppose the resulting sample mean is 19.5 metres. Do you think that this sample result is unusually small? Explain. 答案：We have a random sample of metal rods drawn from a much larger population. A sample mean of only 19.5 metres is about 2.38 standard deviations below what we expect. The sample mean of 19.5 metres is unusually small.