QUESTION
Ch. 2 Exercise 18
Ecommerce.com,
a large Internet retailer, is studying the lead time (elapsed time between
when an order is placed and when it is filled) for a sample of recent orders.
The lead times are reported in days.
Electricity
Cost Frequency
Middle
x-16.45
0 up to 5
6
3
-13.45
180.9025
1085.415
-1067.42
5 up to 10
7
7.5
-8.95
80.1025
560.7175
-508.218
10 up to 15
12
12.5
-3.95
15.6025
187.23
-37.23
15 up to 20
8
17.5
1.05
1.1025
8.82
131.18
20 up to 25
7
22.5
6.05
36.6025
256.2175
-98.7175
Total
40
63
-19.25
314.3125
2098.4
-1580.4
-39.51
a. How Many orders studied.
40
6.285698
mean =
[6*3+7*7.5+12*12.5+8*17.5+8*17.5+7*22.5)/(sum of the freqs) = 16.45
mean =
16.45
12.95
b.
What is the Midpoint of the first class (Round your answer to 1 decimal
place.)
c.
What are the coordinates of the first class for a frequency polygon assuming
we draw a frequency polygon using the midpoints? (Round your answer to 1
decimal place.)
x =
y =
6.29
Variance =
[ 6(3-12.95)^2 + 7(7.5-12.95)^2 + 12(12.5-12.95)^2 + 8(17.5-12.95)^2
+7(22.5-12.95)^2 ] / 40 =
=
40.21
Square root
6.341136
c. Use the
Empirical Rule to estimate the proportion of costs within two standard
deviations
of the
mean. What are these limits?
Lower =
-63.97
Upper =
56.66
ANSWER:
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