In: Statistics and Probability
Shake Shack at the mall is a popular destination with long wait times. Suppose we wish to estimate the wait time for customers at peak dinner time. Assume a previous random sample of size 30 was taken and the sample mean was found to be 14.82 minutes with a sample standard deviation of 4.13 minutes. How large a sample should they take to estimate the true mean wait time to be within 1.2 minutes at the 95% confidence interval?
Given ME = 1.2, Sigma(Standard Deviation) = 4.13, Alpha() = 0.05
The Zcritical at Alpha() = 0.01 is 1.96
The ME is given by :
ME = Z critical * Std Deviation(SD) / Sqrt(n)
Squaring both sides we get: (ME)2 = (Z critical)2 * (SD)2/n
Therefore n = (Zcritical * SD/ME)2 = (1.96*4.13/1.2)2 = 45.5
Therefore n = 46 (Taking it to the next whole number)
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