Math Statistics: Line Graphs

We may represent data using a line graph. A line graph is formed by joining the points given by the data with straight lines.

A line graph is usually used to show the change of information over a period of time. This means that the horizontal axis is usually a time scale, for example minutes, days, months or years.

Example:

The table shows the daily earnings of a store for five days.

a) Construct a line graph for the frequency table.

b) On which days were the earnings above $ 400

Solution:

a)

b) The earnings were above $ 400 on Tuesday and Friday.

Example:

The following line graph shows the total number of animals in a zoo.

a) In which year did the zoo have the largest number of animals?

b) What is the percentage increase of animals in the zoo from 1999 to 2001?

Solution:

a) The zoo had the largest number of animals in 2002

b) The percentage increase of animals in the zoo from 1999 to 2001 is

Multiple sets of related data can also be represented on one line graph.

Example:

The table shows the daily sales in RM of different categories of items for five days.

a) Construct a line graph for the frequency table.

b) On what days were the sales for drinks better than the sales for food?

c) What is the total earnings for food and drinks on Wednesday?

Solution:

a)

b) Sales for drinks were better than sales for food on Thursday and Friday

c) Total earnings for food and drinks on Wednesday is

150 + 350 = $ 500

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