A class measures caterpillar lengths. Ten measurements are: 3, 7, 7, 8, 7, 3, 7, 8, 7, 8 (in centimeters). On a line plot, how many Xs appear above the number 7?
A3
B4
C5
D7
Count the number of times 7 appears in the data: 7, 7, 7, 7, 7 — five times. Each data value gets one X above its position on the number line, and Xs are stacked when the same value appears more than once. So 5 Xs are stacked above the 7. This is the core mechanic of a line plot: one X per data point, stacked to show how many times each value occurs. The height of the stack IS the count.
Question 2 Multiple Choice
A line plot of student heights shows many Xs clustered between 48 and 52 inches, then a gap with no Xs, then two Xs at 60 and 61 inches. What do the two isolated Xs tell you?
AThose two students measured incorrectly and should redo their measurements
BThose values are outliers — isolated data points far from the main cluster that are worth investigating
CThe line plot has a drawing error because values this far apart cannot be in the same data set
DThose two students are the shortest in the class
Outliers are data values that sit far away from the rest of the data, with a gap between them and the main cluster. They don't mean the data is wrong — they mean those values are unusually different from most of the group. On a line plot, outliers are easy to spot because of the visible gap. They are worth investigating: are those students older? Did they measure differently? The line plot makes this visible in a way a list of numbers does not.
Question 3 True / False
On a line plot, a taller stack of Xs above a value means that value appears more often in the data set.
TTrue
FFalse
Answer: True
Each X represents exactly one data point. If the same value appears 5 times, 5 Xs are stacked above it, making a tall column. If a value appears only once, just one X appears. The height of the stack directly shows frequency — how many times each value occurred. This is what makes line plots useful for seeing which values are most common (the tallest stacks) and which are rare (the shortest stacks).
Question 4 True / False
Looking at a list of numbers and looking at a line plot of the same numbers give you equally easy access to information about clusters and gaps in the data.
TTrue
FFalse
Answer: False
A list of numbers can tell you specific values, but it hides the shape of the distribution — where the values cluster, where there are gaps, and which values are outliers. A line plot makes all of this visible at a glance because the positions of the Xs show the spread and the stacks show frequency. For example, the list '3, 7, 7, 8, 7, 3, 7, 8, 7, 8' doesn't immediately show that 7 is the most common value — you have to count. The line plot shows it instantly.
Question 5 Short Answer
A classmate says: 'I can just look at the list of numbers to answer any question about the data — why do I need a line plot?' What does a line plot show that a list of numbers doesn't?
Think about your answer, then reveal below.
Model answer: A line plot shows the shape of the data at a glance: where values cluster, where there are gaps, and which values are outliers. With a list of numbers, you have to count, compare, and search to find these patterns. A line plot organizes the data visually so that the most common values (tallest stacks), unusual values (isolated Xs), and overall spread (range from leftmost to rightmost X) are immediately visible without any counting.
This is the fundamental purpose of data displays: they turn lists of numbers into visual shapes that reveal patterns. Raw numbers require mental effort to compare; a good display does the comparison work for you. The line plot's specific strength is showing distribution — how the data is spread across possible values — which is exactly what you need to answer questions like 'which length was most common?' or 'were there any unusually long caterpillars?' These questions are hard to answer from a list but easy from a plot.