Consider columns 1 and 3 of the energy consumption

2.80 Consider columns 1 and 3 of the energy-consumption data given in Exercise
2.24. Compute the midpoint for each class presented in column 1. Pair each
midpoint with its corresponding relative frequency found in column 3.
Construct a horizontal axis, where the units are in terms of midpoints and a
vertical axis where the units are in terms of relative frequencies. For
each midpoint on the horizontal axis, plot a point whose height is equal to
the relative frequency of the class. Then join the points with connecting
lines. The result is a relative-frequency polygon.
Full file at

46 Chapter 2, Descriptive Statistics
2.81 (a) Consider all three columns of the energy-consumption data given in
Exercise 2.24.
(b) Pair each cutpoint in reworked column 1 with its corresponding
cumulative relative frequency found in reworked column 3. Construct a
horizontal axis, where the units are in terms of the cutpoints and a
vertical axis where the units are in terms of cumulative relative
frequencies. For each cutpoint on the horizontal axis, plot a point
whose height is equal to the cumulative relative frequency. Then join
the points with connecting lines. The result, presented in Figure
(b), is an
ogive
using cumulative relative frequencies. (Note: A
similar procedure could be followed using cumulative frequencies.)
Residential Energy Consumption
0.00
0.05
0.10
0.15
0.20
0.25
35 45 55 65 75 85 95 105 115 125 135 145 155 165
BTU (Millions)
Relative Frequency
Full file at

Section 2.3, Graphs and Charts 47
Residential Energy Consumption
0
0.2
0.4
0.6
0.8
1
1.2
20 30 40 50 60 70 80 90 10
0
11
0
12
0
13
0
14
0
15
0
16
0
BTU (Millions)
Cumulative Relative
Frequency
2.82 (a) After rounding each weight to the nearest integer (Any weight ending in
.5 is rounded up.), the stem-and-leaf diagram for the rounded weights
is
12 9
13 27
14 366
15 011599
16 12567
17 003445689
18 235789
19 1
20 9
21 58
22
23
24
25
26
27 9
(b) After truncating each weight, the stem-and-leaf diagram for the rounded
weights is
12 9
13 26
14 2569
15 01588
16 11557
17 002335588
18 225778
19 1
20 9
21 48
22
23
24
25
26
27 8