Pls help to solve my stastistic question. Thanks alot.?

Question

Steven has been tasked by his company to perform an income study on his customers. The annual incomes of 40 customers randomly selected from his customer base are compiled into a distribition frequency table as follows:

Frequency distribution table (in $'000)

Lower Limit
20
31
41
51
61
71
81
91


Upper Limit
30
40
50
60
70
80
90
100

Count
3
6
8
7
7
5
1
3


Cumulative Count
3
9
17
24
31
36
37
40


%
7.50
15.00
20.00
17.50
17.50
12.50
2.50
7.50


Cumulative %
7.50
22.50
42.50
60.00
77.50
90.00
92.50
100.00

a) Using the class mark, compute the variance and standard deviation.

b) Explain how these statistics can help in Steven's business.

Answer 1

Your data is easier to read this time. The answers haven't changed, though.

Your class marks are 25,35,45,55,65,75,85, and 95

m = 1,000*(3*25 + 6*35 + 8*45 + 7*55 + 7*65 + 5*75 + 1*85 + 3*95) / 40 = 55,750
var = 1,000,000*(3*30.75^2 + 6*20.75^2 + 8*10.75^2 + 7*0.75^2 + 7*9.25^2 + 5*19.25^2 + 1*29.25^2 + 3*39.25^2) / 40 = 356,937,500
sigma = $18,893

Steve can be pretty sure that 25% of his customers earn less than $43,000, and 25% make more than 68,500.

He can gear sales campaigns to reach certain groups

Answer 2

go to office hours. or stay after class for tutoring. or before class.

Answer 3

No.