Lesson 1: Read Line Plots

Property

A line plot is a graph that displays data using marks (such as X’s or dots) placed above a number line. Each mark represents one data value, and multiple marks stacked above the same number show how often that value occurs. In this way, a line plot makes it easy to see the frequency of each value, as well as patterns in the data, such as which values appear most often, which appear least often, and how the data are spread out along the number line.

Examples

• A line plot titled "Number of Books Read in a Month" has a number line from $0$ to $10$. If three students read $5$ books, there would be three X''s above the number $5$.
• A line plot showing "Heights of Seedlings (in cm)" might have a number line from $2$ to $8$. A seedling that is $4\frac{1}{2}$ cm tall would be represented by an X above the $4\frac{1}{2}$ mark on the number line.

Explanation

A line plot is a simple way to organize and see data quickly. It uses a number line to show the range of values in a set of data. Above the number line, X''s or dots are used to mark how many times each value occurs. This makes it easy to see which values are most common, identify the highest and lowest values, and understand the overall distribution of the data.

Property

• Minimum (Min): The smallest numerical value on the number line for which at least one data point (dot or X) is plotted.
• Maximum (Max): The largest numerical value on the number line for which at least one data point (dot or X) is plotted.
• Value with the Greatest Frequency: The value on the number line that has the highest number of data points (dots or Xs) above it.
• Value with the Least Frequency: The value on the number line that has the fewest data points (dots or Xs) above it, excluding values with zero frequency.
• Total Number of Data Points: The sum of all data points plotted on the line plot, representing the overall size of the data set.

Examples

Property

To compare two data points on a line plot, first identify their values on the number line. Then, perform the required operation, such as addition or subtraction, to find their sum or difference.

• Sum: $Value_A + Value_B$
• Difference: $Value_A - Value_B$

Examples

• Find the sum: On a line plot showing the lengths of pencils in inches, the longest pencil is $7\frac{1}{2}$ inches and the shortest is $4\frac{1}{2}$ inches. Their combined length is $7\frac{1}{2} + 4\frac{1}{2} = 12$ inches.

• Find the difference: A line plot shows the amount of juice in cups. If the largest cup has $5\frac{1}{2}$ cups and another cup has $3\frac{1}{2}$ cups, the difference is $5\frac{1}{2} - 3\frac{1}{2} = 2$ cups.