Question

What is the age distribution of promotion-sensitive shoppers? A supermarket super shopper is defined as a shopper for whom at least 70% of the items purchased were on sale or purchased with a coupon.

Age range, years	18-28	29-39	40-50	51-61	62 and over
Midpoint x	23	34	45	56	67
Percent of super shoppers	8%	45%	21%	13%	13%

For the 62-and-over group, use the midpoint 67 years.

(a) Compute the standard deviation σ for ages of super shoppers. (Round your answer to two decimal places.)

ANSWER:?

Answer 1

Solution :

x	P(x)	x * P(x)	x2 * P(x)
23	0.08	1.84	42.32
34	0.45	15.3	520.2
45	0.21	9.45	425.25
56	0.13	7.28	407.68
67	0.13	8.71	583.57
Sum	1	42.58	1979.02

Mean = = X * P(X) = 42.58

(a)

Standard deviation =

=X ² * P(X) - ²

=  (1979.02- 42.58²)

= 12.88