A sample of 50 customers from a large normal population has a mean waiting time of 23 minutes. We know from past testing that the population standard deviation is 4 minutes. Determine a 95% confidence interval for the true mean(waiting time) of the population. Group of answer choices (34.5051, 65.4949) (21.8913, 24.1087) (23.4505, 26.5495) (44.5051, 75.4949)
Confidence interval for Population mean is given as below:
Confidence interval = Xbar ± Z*σ/sqrt(n)
From given data, we have
Xbar = 23
σ = 4
n = 50
Confidence level = 95%
Critical Z value = 1.96
(by using z-table)
Confidence interval = Xbar ± Z*σ/sqrt(n)
Confidence interval = 23 ± 1.96*4/sqrt(50)
Confidence interval = 23 ± 1.1087
Lower limit = 23 - 1.1087 = 21.8913
Upper limit = 23 + 1.1087 = 24.1087
Confidence interval = (21.8913, 24.1087)
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