Grade 8 · Statistics & probability

Scatter plots and bivariate data practice

Scatter plots and bivariate data is a grade 8 math skill aligned to Common Core standard 8.SP.A.1: construct and interpret scatter plots for bivariate measurement data to investigate patterns of association between two quantities. Below are 8 practice questions with answers and step-by-step explanations, drawn from the 22 scatter plots and bivariate data problems our math games drill.

CCSS 8.SP.A.122 questions in the bank
Sample questions

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Question 1easy

In a scatter plot, one point sits far from the pattern of all the others. What is this point called?

A point lying far from the overall pattern is an outlier.

Question 2easy

A scatter plot shows the points (1,2)(1, 2), (2,3)(2, 3), (3,4)(3, 4), (4,5)(4, 5), and (9,20)(9, 20). One point lies far from the pattern of the others. What is the xx-coordinate of that outlier?

The first four points step up steadily, but (9,20)(9, 20) sits far from that pattern, so the outlier's xx-coordinate is 99.

Question 3easy

A scatter plot shows the points (2,10)(2, 10), (3,9)(3, 9), (4,8)(4, 8), (5,7)(5, 7), and (6,1)(6, 1). One point lies far below the pattern of the others. What is the yy-coordinate of that outlier?

The points (2,10)(2, 10), (3,9)(3, 9), (4,8)(4, 8), (5,7)(5, 7) drop by 11 each step, but (6,1)(6, 1) falls far below that pattern, so the outlier's yy-coordinate is 11.

Question 4easy

A scatter plot shows the points (2,3)(2, 3), (3,2)(3, 2), (2,2)(2, 2), (3,3)(3, 3), and (9,9)(9, 9). The points form one tight cluster plus one outlier. How many points are in the cluster?

The points (2,3)(2, 3), (3,2)(3, 2), (2,2)(2, 2), and (3,3)(3, 3) sit close together; only (9,9)(9, 9) is far away. The cluster has 44 points.

Question 5easy

Five students' (hours of sleep, quiz score) data pairs are (6,70)(6, 70), (7,82)(7, 82), (8,88)(8, 88), (5,64)(5, 64), and (9,91)(9, 91). How many of the five students scored above 8080?

The scores above 8080 are 8282, 8888, and 9191, so 33 students.

Question 6easy

A scatter plot shows the points (3,5)(3, 5), (6,4)(6, 4), (2,7)(2, 7), (8,6)(8, 6), and (1,9)(1, 9). For how many of these points is the yy-value greater than the xx-value?

Check each point: 5>35 > 3, 4<64 < 6, 7>27 > 2, 6<86 < 8, 9>19 > 1. The yy-value is greater for 33 points.

Question 7easy

The points (1,4)(1, 4), (2,6)(2, 6), (3,8)(3, 8), and (4,10)(4, 10) on a scatter plot lie on a line. If the linear pattern continues, what is the yy-value when x=5x = 5?

Each step adds 22 to yy, so after (4,10)(4, 10) comes (5,12)(5, 12): y=12y = 12.

Question 8easy

A scatter plot shows the points (1,5)(1, 5), (2,8)(2, 8), (3,11)(3, 11), and (4,14)(4, 14), which lie on a line. Each time xx increases by 11, by how much does yy increase?

From 55 to 88 to 1111 to 1414, yy goes up by 33 each time xx goes up by 11.

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