8th Grade Scatter Plots and Association Worksheet Solutions (PDF)
This grade 8 scatter plots answers for 8th Grade covers scatter plots and association (Common Core 8.SP.A.1, 8.SP.A.2), with a free PDF to print.
This answer key gives a full worked solution for each of the 21 problems on the scatter plots and association worksheet (Common Core 8.SP.A.1 and 8.SP.A.2). Compare each step with your own work, not only the final answer, and note any step where your method differed.
Grade 8 · Common Core State Standards: 8.SP.A.1, 8.SP.A.2
Grade 8 scatter plots answers: exercises 1 to 10
Exercise 1 – Plot the data
The explanatory variable (hours) goes on the x-axis and the score goes on the y-axis.
Points (1, 52), (2, 58), (3, 63), (4, 67)
Exercise 2 – Describe the association
As the hours increase, the scores tend to increase, and the points are near a line.
Positive, linear, strong
Exercise 3 – Three plots
Left: rising points. Middle: falling points. Right: no pattern.
Positive, negative, no association
Exercise 4 – Find the outlier
The first seven points rise steadily, but (8, 3) is far below the pattern.
(8, 3)
Exercise 5 – Linear or nonlinear
The points rise and then fall, forming a curve. They do not follow a straight line.
Nonlinear
Exercise 6 – Shoe size and height
Taller people usually have bigger feet, so both tend to increase together.
Positive association
Exercise 7 – Cocoa sales
On colder days more cocoa is sold, so as the temperature rises, sales fall.
Negative association
Exercise 8 – No association
There is no reason for the month to influence the score, so the points would show no pattern.
No association
Exercise 9 – Clusters
One group is near (2, 3) and the other near (8, 8). There is no cluster in the middle.
Two clusters
Exercise 10 – Trend line slope
\(\frac{90 – 52}{8 – 1} = \frac{38}{7} \approx 5.4\).
About 5.4: each extra hour of study adds about 5.4 points
Exercises 11 and up
Exercise 11 – Equation of a trend line
At \(x = 2\): \(5.3 \cdot 2 + 47 = 57.6\), close to 58.
At \(x = 6\): \(5.3 \cdot 6 + 47 = 78.8\), close to 79.
Yes, the line is close to both points
Exercise 12 – Predict
\(y = 5.3 \cdot 7 + 47 = 37.1 + 47 = 84.1\).
about 84
Exercise 13 – Car value
As the age increases, the value decreases. The points follow a line.
Negative, linear
Exercise 14 – Compare two lines
At \(x = 8\): A gives 89.4, near the data point 90. B gives 64, far below 90.
Line A fits better
Exercise 15 – Ice cream sales
As the temperature rises, the number of cones sold rises in a nearly straight pattern.
Positive linear association
Exercise 16 – Ice cream trend line
\(y = 1.2 \cdot 100 – 53 = 67\).
about 67 cones
Exercise 17 – Basketball practice
Both increase together, positive association.
Slope \(= \frac{18 – 8}{50 – 10} = 0.25\) more free throws per minute.
Positive; slope about 0.25
Exercise 18 – Effect of an outlier
The outlier pulls the line down, so the line does not follow the steady rise of the other points.
The outlier distorts the trend line
Exercise 19 – Cause and effect
No. Both increase with age, so age explains the association. Association does not prove causation.
No; age is a hidden factor
Exercise 20 – Choose the best description
Falling points mean negative, and points close to the line mean strong.
(b) strong negative
Exercise 21 – Explain a good fit
Most points are close to the line, and the points are spread above and below the line in about equal numbers.
Points near the line, balanced above and below
Key facts behind this grade 8 scatter plots answers
- Positive association: as x increases, y tends to increase.
- Negative association: as x increases, y tends to decrease.
- Clusters are groups of points; outliers are points far from the pattern.
- A linear association has points near a straight line; nonlinear follows a curve.
- A trend line has about as many points above as below and is close to the points.
How to use this grade 8 scatter plots answers
Cover each solution, solve the exercise again, then uncover it and compare every line. If your answer differs, find the first step that changed and redo the exercise from there.
Download the grade 8 scatter plots answers as a PDF with the button below and keep it with your notes.
All Grade 8 chapters: Grade 8 math.
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