Dot Plot
In short: Dot plot shows each data value as a dot stacked above a number line, so you can see clusters, gaps and the most common values at a glance.
6th GradeStatistics6.SP.B.4
What is Dot Plot?
A dot plot is the simplest picture of a small data set. Draw a number line, and every time a value appears in the data, add one dot above it. Tall stacks mean popular values and empty spaces mean nobody had that value.
Precisely, if 14 students report how many books they read, the dots for all values total 14. From the plot you can read the count of any value, the largest and smallest values, the range, the center and the overall shape.
How to spot it
- A data set has fewer than about 30 values that are whole numbers or simple measurements.
- A graph shows dots piled above a labeled number line, with each dot standing for one item.
- A question asks which value occurs most often, or whether there is a gap or a lone far-away dot.
- You are asked to compare how data are spread out, not just a single average.
The method
- Draw a number line that covers the smallest to the largest value, with equal spacing.
- For each data value, put one dot above its place on the line, stacking dots when a value repeats.
- Title the plot and label the line with the quantity and its unit.
- Read the picture: find the tallest stack, any gaps, the highest and lowest values and the middle dot.
Dot Plot: solved example
Problem
A dot plot shows the number of siblings of 20 students. The dots are: 0 siblings (3 dots), 1 sibling (8 dots), 2 siblings (6 dots), 3 siblings (2 dots), 5 siblings (1 dot). How many students have at least 2 siblings, and what is the most common value?
Solution
At least 2 means the stacks at 2, 3 and 5: \(6 + 2 + 1 = 9\) students.
The tallest stack is at 1 sibling with 8 dots. So 9 students have at least 2 siblings, and the most common value is 1.
Try it
Question 1
A plot has dots at 4, 4, 5, 5, 5, 6, 9. How many values are there, and is there a gap?
Show the answer
Seven values. There is a gap from 6 to 9, where no dots appear.
Question 2
Build a plot from the data 2, 3, 3, 4, 4, 4. How many dots are above 4?
Show the answer
Three dots, because 4 appears three times.
Dot Plot vs. Histogram
A dot plot keeps every single value as its own dot, so it works for small sets and shows exact numbers. A histogram groups values into intervals and shows bars, which suits larger sets where counting each dot would be unwieldy.
Keep going
Lessons
Worksheets and quizzes
- Statistical Questions and Data Displays – Worksheet
- Statistical Questions and Data Displays – Quiz
- Mean, Median, Spread and Box Plots – Worksheet
- Mean, Median, Spread and Box Plots – Quiz
Related words
Whole dictionary: A–Z · 6th Grade · Statistics