Download Statistics and Probability 8.SP.3

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Pomona Unified Math News
th
Domain: 8 Grade Statistics and Probability (SP)
8.SP.3: Use the equation of a linear model to solve problems in the context of bivariate measurement data,
interpreting the slope and intercept. For example, in a linear model for a biology experiment, interpret a slope of
1.5 cm/hr as meaning that an additional hour of sunlight each day is associated with an additional 1.5 cm in
mature plant height.
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Suggested Standards for Mathematical
Practice (MP):
MP 2 Reason abstractly and quantitatively.
MP.4 Model with mathematics.
MP.5 Use appropriate tools strategically.
MP.6 Attend to precision.
MP.7 Look for and make use of structure.
Number
of
Absences
3
5
1
1
3
6
5
3
0
7
8
2
9
0
6
6
2
0
5
7
9
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Explained in 8.SP.1
Vocabulary:
(Note: vocabulary will be taught in the context
of the lesson, not before or separate from the
lesson.)
Correlation/association: See 8.SP.1
Bivariate data: See 8.SP.1
Scatter plot: See 8.SP.1
Outlier: See 8.SP.1
Linearity: See 8.SP.1
Line of best fit: See 8.SP.2
Explanations and Examples:
Example 1:
Given data from students‘ math scores and
absences, make a scatterplot to see if there may
be a relationship between the two.
Math
Scores
65
50
95
85
80
34
70
56
100
24
45
71
30
95
55
42
90
92
60
50
10
80
Example 2:
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Adapted from Georgia Math Grade 8 flip
book and www.mathisfun.com
Draw a line of best fit, paying attention to
the closeness of the data points on either
side of the line.
Solution:
!
!
Pomona Unified Math News
th
Domain: 8 Grade Statistics and Probability (SP)
8.SP.3: Use the equation of a linear model to solve problems in the context of bivariate measurement data,
interpreting the slope and intercept. For example, in a linear model for a biology experiment, interpret a slope of
1.5 cm/hr as meaning that an additional hour of sunlight each day is associated with an additional 1.5 cm in
mature plant height.
this relates to the graph.
Students informally draw a line of best fit for a
scatter plot and informally measure the strength
of fit. Discussion should include “What does it
mean to be above the line, below the line?”
From the line of best fit, determine an
approximate linear equation that models the
given data.
Solution: 𝒚 = −
𝟐𝟓
𝟑
𝒙 + 𝟗𝟓
Students should recognize that 95 represents
the y intercept (where the line of best fit
crosses the y axis) and −25/3 represents the
slope of the line. (This can be determined by
finding the slope between any two points) The
slope can vary slightly.
Students can use this linear model to solve
problems. For example, through substitution,
they can use the equation to determine that a
student with 4 absences should expect to
receive a math score of about 62. They can
then compare this value to their line.
The study of the line of best fit ties directly to
the algebraic study of slope and intercept.
Students interpret the slope and intercept of the
line of best fit in the context of the data. Then
students can make predictions based on the line
of best fit.
Common Misconceptions:
See standard 8.SP.1
Web Help Links (Use a QR scanner to take
you directly to the website)
https://learnzillion.com/resources/51621
https://learnzillion.com/resources/51624
Instructional Strategies:
Scatter plots are the most common form of
displaying bivariate data in Grade 8. Students
should be provided scatter plots and have
student’s practice informally finding the line of
best fit. Students should create and interpret
scatter plots, focusing on outliers,
positive or negative association, linearity or
curvature. By changing the data slightly,
students can have a rich discussion about the
effects of the change on the graph. Students
should have use of a graphing calculator to
determine a linear regression and discuss how
https://learnzillion.com/resources/51166