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Assume that the helium porosity (in percentage) of coal samples taken from any particular seam is normally distributed with true standard deviation :75.

a. Compute a 95% CI for the true average porosity of a certain seam if the average porosity for 20 specimens from the seam was 4:85.

b. How large a sample size is necessary if the width of the 95% interval is to be :40?

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Category:- Statistics and Probability
Reference No.:- M91001760

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