You measure 8 pencils and find that 3 pencils are exactly 6 inches long. When you make a line plot, what do you put above the number 6 on the number line?
AThe number 3, to show that three pencils had that length
BThree X's, one for each pencil that measured 6 inches
COne X, because 6 inches is just one measurement value
DA bar reaching up to 3, like a bar graph
In a line plot, each X represents one individual object or measurement — not a count. Three pencils measured 6 inches, so you place three separate X's above the 6, stacked on top of each other. This is the most common confusion when building line plots: students want to write the number '3' instead of three X marks. The height of the stack shows the count; each X itself represents one data point.
Question 2 Multiple Choice
A class measures 10 crayons and gets these lengths in inches: 4, 5, 4, 6, 5, 4, 5, 6, 4, 5. What does the tallest stack of X's on their line plot show?
AThe longest crayon in the set
BThe total number of crayons measured
CThe most common crayon length (the mode)
DThe average crayon length
The tallest column of X's marks the value that appears most often in the data — the mode. In this data set, 4 inches appears 4 times and 5 inches appears 4 times, so those two values would tie for tallest column. The tallest stack does NOT show the longest measurement (that's the rightmost value on the number line) or the total count (that's all X's added together).
Question 3 True / False
On a line plot, the number line should begin at zero.
TTrue
FFalse
Answer: False
The number line on a line plot should span from the smallest value in the data set to the largest — it does not need to start at zero. If the shortest measurement is 4 inches and the longest is 7 inches, the number line should run from 4 to 7. Starting at zero would waste space and make the data harder to read. What matters is that the intervals between tick marks are consistent.
Question 4 True / False
In a line plot displaying measurement data, each X represents exactly one object that was measured.
TTrue
FFalse
Answer: True
This is the defining rule of a line plot: one X per data point, placed above the matching value on the number line. If you measured 10 pencils, your finished line plot will have exactly 10 X's total, no matter how the measurements are distributed. This one-to-one correspondence between marks and measurements is what distinguishes a line plot from other displays.
Question 5 Short Answer
Why is it important that the intervals between numbers on a line plot's number line are equally spaced?
Think about your answer, then reveal below.
Model answer: Because unequal spacing distorts the visual picture of the data. If the gap between 4 and 5 is twice as wide as the gap between 5 and 6, the display makes those values look farther apart than they really are, which misleads anyone reading the graph. Equal spacing ensures that distances on the number line accurately represent the numerical differences in the measurements.
The scale is the backbone of the graph; if it's inconsistent, the visual patterns it shows are unreliable. Students who understand this can identify when a display is misleading, not just when it is technically correct.