The manager of The Cheesecake Factory in Boston reports that on six randomly selected weekdays, the number of customers served was 175, 125, 180, 220, 240, and 245. She believes that the number of customers served on weekdays follows a normal distribution. Construct the 99% confidence interval for the average number of customers served on weekdays.
Question
Answer:
(121.576 ; 273.424)
Step-by-step explanation:
Given the data:
175, 125, 180, 220, 240, 245
We can calculate the mean and standard deviation
Mean = Σx/ n = 1185 / 6 = 197.5
Standard deviation = 46.125 (calculator)
The confidence interval :
Mean ± margin of error
Margin of Error = Tcritical * s/sqrt(n)
Tcritical at 99%, df = n – 1 ; 6 – 1 = 5
Tcritical = 4.032
Margin of Error = 4.032 * 46.125/√6
Margin of error = 75.924
Confidence interval :
197.5 ± 75.924
Lower boundary = 197.5 – 75.924 = 121.576
Upper boundary = 197.5 + 75.924 = 273.424
(121.576 ; 273.424)