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Daily Math Minute

Measurement & Data

Line Plots

Generating measurement data and displaying it on a line plot.

Foundational15 min lesson2 min readUpdated August 12, 2026Author not yet attributed

Plotting Individual Measurements

A scaled bar graph groups data into categories. A line plot displays something different: individual measurements, like the lengths of several pencils, each marked directly above its value on a number line.

Definition — Line Plot

A graph showing data along a number line, with a mark (often an X) placed above each data point's value — stacking marks when the same value occurs more than once.

To build a line plot, first draw a number line covering the range of the data, including fraction values when measurements aren't whole numbers. Then, for each measurement, place one mark directly above its value on the line.

Worked Example — Reading a Line Plot

A line plot of pencil lengths (in inches) has 2 marks above 3, 1 mark above 3 1/2, and 3 marks above 4. How many pencils were measured in all? Add the number of marks: 2 + 1 + 3 = 6. Six pencils were measured.

Worked Example — Answering a Question from a Line Plot

Using the same line plot (2 marks at 3, 1 mark at 3 1/2, 3 marks at 4 inches), how many pencils measured longer than 3 inches? Count the marks above values greater than 3: 1 mark at 3 1/2 plus 3 marks at 4, giving 1 + 3 = 4 pencils.

Tip

Line up every mark carefully with the number line's scale — a mark placed even slightly off its true value makes the line plot misleading to read.

Common Mistakes

  • Placing marks for repeated values side by side instead of stacked directly above the same point.

    Every mark for the same measured value must stack directly above that one point on the number line, not spread out sideways.

  • Leaving out fraction values on the number line's scale when the data includes fractional measurements.

    Mark the number line with the same fraction intervals the data actually uses, such as halves or fourths, so every measurement has an exact place to be plotted.

Key Takeaways

  • A line plot shows individual measurements as marks above their value on a number line.
  • Repeated values stack marks directly above the same point.
  • A line plot's number line must include any fraction values the data actually uses.

Summary

Line plots display real measured data directly on a number line, connecting data display back to the fraction number line from earlier in this grade. The final unit returns to geometry, reasoning more deeply about how shapes relate to one another.

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