Posted by **Lynn** on Wednesday, June 13, 2012 at 8:38pm.

A purchasing agent wants to estimate the mean daily usage of rye flour. She takes a sample for 50 straight days and find that the sample mean is 180 lbs with a sample standard deviation of 38.5 lbs. a)State the 90% confidence interval for the mean.b) State the margin of error

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**MathGuru**, Thursday, June 14, 2012 at 7:16pm
Use a confidence interval formula:

CI90 = mean ± 1.645(sd/√n)

...where ± 1.645 represents the 90% confidence interval using a z-table, sd = standard deviation, √ = square root, and n = sample size.

Plug your data into the formula to calculate the confidence interval and the margin of error.

I hope this will help get you started.

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