Represent and Interpret Data – Line Plot

Key Concepts

• Organizing the data
• Making line plot
• Measurement data in line plot to solve problems

Introduction

In this chapter, we will learn how to organize data, make a line plot and measure data in line plots to solve problems. 

Make line plots 

• A line plot is a graph that displays data using a number line.  
• Line plots are also called dot plots. 

The image below is an example of a line plot. 

Organizing the data  

Organizing data is bringing it together in a systematic way that makes it easier to read. 

• Data can be organized using tallies and frequency tables. 
• Tallies are a way of counting by drawing a short vertical line to record each item. 

Example 1:  

Following is the data of weights collected during the medical check-up of 35 students of a class: 

Step 1: Write the weights from least to greatest. 

Step 2: Organize data in a frequency table. 

Example 2: 

The kids in a daycare centre have the following weights. How can you organize this information? 

Step 1: Write the weights from least to greatest. 

Step 2: Organize the data in a frequency table. 

Making line plot

• To make a line plot, ​first, create a number line that includes all the values in the data. 
• Place an X (or dot) above each data value on the number line. 
• A value occurs more than once in a data set. Place ​an X over that number for each time it occurs. 

Example 1: 

The following table shows the number of ribbons of each length. Create a line plot for this data. 

Step 1: Draw the number line using an interval of 1. 

Step 2: Mark x for each value in the data set.  

Step 3: Write the title for the line plot. 

Example 2: 

David measured the lengths of his friends’ hands. He records the measurements in the table below. 

Make the line plot using David’s data. 

Solution: 

Step 1: Draw the number line using an interval. 

Step 2: Mark x for each value in the data set.  

Step 3: Write the title for the line plot.

Measurement of data in line plot to solve problems 

Example 1:  

The heights of Sabrina’s dolls are shown below. 

1. How many dolls are taller than 22 centimetres? 

2. How many dolls are 24 centimetres? 

3. How many total dolls are there? 

Solutions: 

1. 5 dolls 

2. 3 dolls 

3. 14 dolls 

Example 2: 

The line plot shows the length of sticks in inches. Use the line plot to answer the questions. 

1. How many sticks are 2 inches long? 

2. What is the length of most of the sticks? 

3. How many sticks are 3 inches long? 

Solution: 

1. 2 sticks 

2. 1 inch 

3. 1 stick 

Exercise

1. The following data points represent the number of trick-or-treaters James had each year since he started putting pumpkins in his yard. Organize the data in a frequency table. 54, 56, 53, 54, 56, 55.

2. The following dot plot shows the daily high temperature in Key West, Florida, in April. Each dot represents a different day. How many days had a temperature of at least 16 °C?

3. Quarterback Susie has a bad attitude and often gets fined for bad sportsmanship. Below are the costs of each of the six fines assessed to her this season in thousands of dollars)

Using this data, make a plot.

4. Keta is asked to collect data for the size of shoes of students in her Class VI. Her finding is recorded in the manner shown below:

Organize the given data in a frequency table.

Concept Map 

What have we learned

• Understanding line plots
• How to organize the data
• How to make the line plots using data
• How to solve word problems using measurement data