Construct and Interpret Scatter Plots

Students plot bivariate data on a scatter plot, labeling axes with variable names and units. They describe the pattern of association as positive, negative, or no association, and linear or nonlinear, and identify outliers that deviate from the overall pattern.

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Grade 8 · Statistics and Probability: Bivariate Data · question 1 of 3

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20 rungs. A star at the top.

The scatter plot shows how many books students read this year against their number of siblings. How many siblings does the student marked B have?

Your answer:

How it is taught

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A scatter plot shows paired data as dots.

Association is the pattern those dots make; an outlier sits off that pattern.

Read it: Reading a scatter plot

Each dot is one player: across is the hours practiced, up is the points scored. Dot A is at 6 hours and 12 points. As the hours grow, the points tend to grow too: a positive association.

Read a dot: straight down to the x axis, then straight across to the y axis.
Count dots against a value: the ones on its line and the ones past it.
Read the cloud left to right: climbing is positive, falling is negative, neither is no association.

Each dot holds two numbers about one thing, so the plot shows how the two go together.

A trend is what the dots tend to do: a few dots against it do not change it.

An association is not a cause: two things can grow together for some other reason.

A dot is (across, up). A cloud that climbs is a positive association, one that falls is negative.

Reading A's hours, 6, as its points.

Go straight across from A to the y axis: 12 points.

For each day, the outside temperature and the number of hot drinks a café sells: warmer days tend to sell fewer. Which association is that? — negative association. As one grows, the other tends to shrink.

Hours studied vs. test score (8 students)

We tracked eight students: how many hours each studied, and the score they got on the test.

Draw two axes. Hours studied runs along the bottom, and test score goes up the side.

The first student studied one hour and scored fifty-five. Move right to one, up to fifty-five, drop a dot.

Plot the next six students the same way, one dot for each pair.

Here's the last student: three hours studied, but only thirty points.

Step back. As hours go up, scores tend to go up too — that's a positive association.

The dots roughly follow a straight line, so we call this pattern linear.

But one dot sits way below the rest. That point is an outlier — it doesn't fit the trend.

Grade 8 · Plot bivariate data and read the pattern

Our scatter plot shows a positive, linear association — with one outlier. Nice work reading the data!

What you see

While they climb, your page writes one true line to ask about tonight, and a short note each Sunday.

MayaGrade 3 · Mathematics

Did you know?

A chessboard has 64 squares — share them out between the 8 rows and each row holds exactly 8.

Today’s goal: 1 star — one skill mastered, every rung of its ladder climbed
Climbing now: Divide within 100

An example student.

MayaGrade 3 · Mathematics

Maya earned 2 stars this week — Interpret multiplication as equal groups, which took 6 answers over 3 days before its star landed 3 days ago and Multiply by 6, 7, 8 and 9. Next up: Divide within 100.

An example week.

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