Line Plots and Data Analysis

What Is a Line Plot?#

A line plot (also called a dot plot) is a graph that shows data along a number line. Each piece of data is represented by an X (or a dot) placed above the corresponding value on the number line. Line plots are especially useful for showing the distribution of data — how data values are spread out.

When to Use a Line Plot#

Line plots work best when you have:

• A set of numerical data (not categories)
• Data that falls within a limited range
• Data that you want to show every individual value

Line plots are commonly used in Grade 4 to display measurement data — heights, lengths, temperatures, or times — often recorded in fractions.

Reading a Line Plot#

To read a line plot:

1. Look at the number line along the bottom — this shows the possible data values
2. Count the X marks above each value — each X represents one measurement
3. The value with the most X marks is the mode (most frequent)
4. Notice any gaps or clusters in the data

Example Line Plot#

Heights of bean plants (in inches) after two weeks:

X
X   X
X   X   X
X   X   X   X
─────────────────
2   3   4   5   6

Reading: 4 plants are 2 inches, 3 are 3 inches, 3 are 4 inches, 2 are 5 inches, 0 are 6 inches.

Questions you can answer:

• How many plants total? Count all X's: 12 plants
• What is the most common height? 2 inches (4 X's)
• What is the range? 5 − 2 = 3 inches