Line Plot

How to line plot, step by step: the rule in plain language, solved examples worked one line at a time, and practice questions so you can try it yourself before moving on.

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A line plot (also called a dot plot) is a simple graph that shows data values on a number line, with an X or dot placed above each value every time it appears. Line plots make it easy to see the distribution of a data set — which values are most common, where the data clusters, and whether there are gaps or outliers. They appear frequently on the GED Math test in data and statistics problems.

What Is a Line Plot?

A line plot consists of:

A horizontal number line showing all possible values in the data range
An X (or dot) placed above a value for each time that value appears in the data set
A title and label for the number line

The height of the stack of X’s above a number shows its frequency (how many times it appears).

How to Read a Line Plot

Interpreting the display

Count the X’s above each number to find its frequency.
The number with the most X’s is the mode.
Add up all the X’s to find the total number of data values.
You can find the median by counting to the middle X, and the range by subtracting the smallest labeled value from the largest labeled value.

How to Make a Line Plot

Step-by-step process

Find the minimum and maximum values in the data set.
Draw a number line that spans from the minimum to the maximum, labeling every integer in between.
For each data value, place an X above the corresponding number on the line.
Stack X’s vertically if a value appears more than once.
Add a title and label to the number line.

Step-by-Step Summary

Identify the range of values and draw a number line.
Place one X above each value for each time it appears.
To read: count X’s for frequency; find mode, median, and range from the plot.

Watch: How to Make a Line Plot (Video Lesson)

Math with Mr. J shows you exactly how to create a line plot with whole numbers:

Worked Examples

Example 1: The data set {2, 3, 3, 4, 4, 4, 5, 6} is displayed on a line plot. How many X’s appear above the number 4? What is the mode?

3 X’s appear above 4 (it appears 3 times). Mode = 4

Example 2: A line plot shows ages of students: the numbers 8, 9, 10, 11 appear on the number line. The X counts are: 8 → 2, 9 → 5, 10 → 3, 11 → 1. What is the total number of students? What is the range?

(color{blue}{text{ Total } = 2 + 5 + 3 + 1}) = 11 students; (color{blue}{text{ Range } = 11 – 8}) = 3

Example 3: Create a line plot for: 5, 7, 5, 8, 9, 7, 7, 6.

Number line: 5, 6, 7, 8, 9
X counts: 5 → XX, 6 → X, 7 → XXX, 8 → X, 9 → X
Mode = 7 (3 X’s); (color{blue}{text{ Range } = 9 – 5 = 4})

Example 4: Using the line plot from Example 3, what is the median?

All 8 values in order: 5, 5, 6, 7, 7, 7, 8, 9
(color{blue}{text{ Median } = (7 + 7) div 2}) = 7

More Practice: Introduction to Line Plots (Video)

Khan Academy introduces line plots and how to use them to answer questions:

Exercises

Data: 3, 4, 4, 5, 5, 5, 6, 7. Which value is the mode?
A line plot has values 10–15. The X counts are: 10(1), 11(3), 12(4), 13(2), 14(1), 15(1). How many total data points are there?
Using the line plot in #2, what is the mode?
Create a line plot for: 1, 2, 2, 3, 3, 3, 4. How many X’s are above 3?
A line plot shows: 8(2 X’s), 9(4 X’s), 10(3 X’s), 11(1 X). What is the range? What is the mode?

Answers

5 (appears 3 times)
(color{blue}{1+3+4+2+1+1}) = 12 data points
12 (4 X’s, the most)
3 X’s above 3 (appears 3 times)
(color{blue}{text{ Range } = 11 – 8}) = 3; Mode = 9 (4 X’s)

Statistics for Beginners The Ultimate Step by Step Guide to Acing Statistics

Frequently Asked Questions

What is a line plot in math?

A line plot is a graph that shows data on a number line, with an X or dot placed above a value each time it appears. If five students have 2, 3, 3, 3 and 5 pets, you put one X above 2, three above 3 and one above 5. The tallest stack shows the mode, which here is 3 pets.

What is a line plot in 3rd grade?

In 3rd grade, students use line plots to show measurement data, often lengths measured to the nearest half or quarter inch. A class might measure pencils and mark each length above a number line labeled 4, 4½, 5, 5½ and 6 inches. Students then answer questions such as how many pencils are longer than 5 inches.

How do you make a line plot with fractions?

Divide the number line into equal fractional steps that match your data, such as quarters or eighths. For the lengths 1/4, 1/2, 1/2, 3/4 and 1 inch, label the line 0, 1/4, 1/2, 3/4, 1 and put an X above each value. Then you can combine or compare values; for example, the two 1/2-inch pieces add up to 1 inch.

How do you make a line plot?

Find the smallest and largest data values, draw a number line that covers that range with equal spacing, and mark an X above a value each time it occurs. Stack repeated X’s neatly so the columns are easy to compare. Finish with a title and a label for the number line, such as Hours of Sleep.

What is a line plot example?

Suppose 9 students record how many miles they walked in a week: 1, 2, 2, 3, 3, 3, 3, 4, 6. The line plot has one X above 1, two above 2, four above 3, one above 4 and one above 6. From it you can read the mode (3), the median (the 5th value, 3) and the range (6 − 1 = 5). The gap at 5 also stands out.

What is the difference between a line plot and a line graph?

A line plot uses X’s or dots stacked above a number line to show how often each value appears in one data set. A line graph connects points with line segments to show how something changes over time, like the temperature recorded every hour. Use a line plot for counting data and a line graph for showing trends.

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