Show me your work Ferric chloride is used as a flux in some types of extraction

Question

Show me your work Ferric chloride is used as a flux in some types of extraction metallurgy processes. This material is shipped in containers, and the container weight varies. It is important to obtain an accurate estimate of mean container weight. Suppose that from long experience a reliable value for the standard deviation of flux container weight is determined to be 4 lb. How large a sample would be required to construct a 95% two-sided confidence interval on the mean that has a total width of 1 lb?

Explanation / Answer

Standard deviation of flux cont. = 4 lb

Z for 95% confidence is given by : 1.96

We need to have a sample size n , for which the amrgin of error is of width = 1lb

So, margin of error = MOE = 2*Z*sigma/sqrt(n) = 1

1.96*2*4/sqrt(n) = 1

n = (1.96*2*4)^2 = 61.44 or 62 to round off to integer

n = 62 will be the sample size

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