Over a two-year period, a convenience store recorded the number of monthly sales
ID: 3322671 • Letter: O
Question
Over a two-year period, a convenience store recorded the number of monthly sales which involved the purchase of a soda. The monthly average is 506.3 and standard deviation is 272.9. Consider the number of sales that involve soda to be unusual if the z-score is less than -2.00 or greater than 2.00. Determine if 298 sales of soda per month is unusual.
(A) The z-score is 0.76. It WOULD be considered unusual for 298 sales involving the purchase of soda in one month.
(B) The z-score is 0.76. It WOULD NOT be considered unusual for 298 sales involving the purchase of soda in one month.
(C) The z-score is -0.76. It WOULD NOT be considered unusual for 298 sales involving the purchase of soda in one month.
(D) The z-score is -0.76. It WOULD be considered unusual for 298 sales involving the purchase of soda in one month.
Explanation / Answer
mean = 506.3
std. dev. = 272.9
xbar = 298
using central limit theorem,
z = (xbar - mean)/(std.dev.)
z = (298 - 506.3)/272.9
z = -0.7633
The z-score is -0.76. It WOULD NOT be considered unusual for 298 sales involving the purchase of soda in one month.
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