dispersion
2011-06-12 6:53 am
The lengths of pencils produced by a machine are normally distributed. If the upper limit of the standard length of a pencil is 16.97cm and its lower limit is 16.73cm, 2.5% of the pencils are regarded as too long and 2.5% are too short. Find the mean and standard deviation of the lengths of the pencils.
回答 (1)
2011-06-12 6:55 am
✔ 最佳答案
µ + 1.96σ = 16.97µ - 1.96σ = 16.73
So, 2µ = 33.7
µ = 16.85 and σ = 0.06122
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