Confidence interval = mean ± margin of error
CI90 = mean ± 1.645 (sd/√n)
With your data:
CI90 = 180 ± 1.645 (38.5/√50)
I'll let you take it from here.
A purchasing agent at the Kelly Bread Company wants to estimate the mean daily
usage of rye flour. She takes a sample for 50 straight days and finds that the sample
mean is 180 pounds with a sample standard deviation of 38.5 pounds.
a)
State the 90% confidence interval for the mean.
(Round to hundredths)
b)
State the margin of error
(Round to tenths)
1 answer