Question

The table shown below details the observed amount of electricity consumed by the average American over the course of one year, as measured in kilowatt-hours.
Month
Usage (kWh)
Jan-Feb
2,239
Mar-Apr
2,197
May-Jun
2,113
Jul-Aug
2,156
Sep-Oct
2,269
Nov-Dec
2,270

Kevin is trying to display this information in the form of a graph. He would like the graph to look like the one below.
A line graph titled energy consumption per capita. The line decreases, and then increases. The x- and y-axes are not labeled.
What scale should Kevin use on the y-axis to display the information on the table like the graph?
a.
500 kWh per mark
b.
100 kWh per mark
c.
50 kWh per mark
d.
10 kWh per mark

Answer 1

First find the range: max − min = 2,270 − 2,113 = 157 kWh.

We need a scale that shows that 157 kWh change clearly (several tick marks).
- 500 kWh/mark → 0.314 marks (no visible change)
- 100 kWh/mark → 1.57 marks (barely visible)
- 50 kWh/mark → 3.14 marks (clearly shows decrease then increase)
- 10 kWh/mark → 15.7 marks (unnecessarily many ticks)

So 50 kWh per mark is the best choice. Answer: c.