Grade 8 Lines of Best Quiz with Answers – Free PDF

Contents

This grade 8 lines of best quiz asks 10 multiple-choice questions on lines of best fit and linear models, and each answer comes with a short explanation.

Ten multiple-choice questions check your skill with lines of best fit: judging fit, finding slope and equations, interpreting slope and intercept, and spotting outliers. Pick the one correct answer, then read the explanation to learn from any mistake.

Grade 8Common Core: 8.SP.A.2 · 8.SP.A.3

🎯 Lines of Best Fit and Linear Models – Grade 8 math quiz

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Answered: 0 / 10

Question 1

Which statement best describes the fit of the line to the plant data?

Plant height and days since planting.

A Poor fit: the line misses some points

B Poor fit: the points should lie on a curve

C Good fit: every point is exactly on the line

D Good fit: the points are close to the line

Question 2

What is the slope of the line through the two labeled points?

A line through two points.

A $\frac{1}{3}$

B $3$

C $4$

D $12$

Question 3

A line of fit has slope 4 and passes through $(3,20)$. What is its equation?

A $y=4x+8$

B $y=4x+12$

C $y=4x+20$

D $y=3x+20$

Question 4

The cost of renting skates is modeled by $C=2.5h+15$, where $h$ is hours. What does 2.5 mean?

A The rental costs $2.50 in total

B Each extra hour costs $2.50

C The fixed fee is $2.50

D The skates are rented for 2.5 hours

Question 5

In $C=2.5h+15$, what does the y-intercept 15 mean?

A The cost rises $15 each hour

B The skates are rented for 15 hours

C The cost is $15 before any hours are added

D The cost is $15 after 1 hour

Question 6

Use $C=2.5h+15$ to predict the cost of renting skates for 4 hours.

A $10

B $17.50

C $40

D $25

Question 7

Is a straight line a good model for the data shown?

Height of a ball over time.

A No, the points curve instead of following a line

B Yes, the line passes through two points

C Yes, the points mostly go up

D No, because the line has a positive slope

Question 8

Which point is the outlier?

Free throws made over 8 weeks.

A $(1,14)$

B $(8,33)$

C $(6,12)$

D $(4,23)$

Question 9

Noah's training time fits $T=-0.5w+30$, where $T$ is minutes and $w$ is weeks. For which $w$ does the model predict 24 minutes?

A $w=6$

B $w=3$

C $w=-12$

D $w=12$

Question 10

A model is built from data for $x=2$ to $x=10$. Which prediction is least reliable?

A $x=5$

B $x=7$

C $x=40$

D $x=9$

🎉 Quiz complete!

0 / 10

How does this quiz work?

Read each question, choose one answer among A, B, C and D, then check it: a short explanation appears after every answer. Your score out of 10 is shown at the end, and you can restart the quiz as often as you like.

What should you review before the quiz?

Reread the key facts of the lesson and the worked example. If a question is hard, go back to the matching part of the lesson, then try the quiz again. Write your work on scrap paper: most mistakes come from skipping a step, not from the idea itself.

Remember:

Standards 8.SP.A.2 and 8.SP.A.3: fit a line informally, judge the fit, and interpret the equation of a linear model.
A good line has points close to it on both sides; a curve or wide scatter means a line is a poor model.
Slope = change in y per 1 unit of x; y-intercept = predicted y when x = 0.
Find the equation from two points on the line, not necessarily data points.
Predictions inside the data range are more reliable than predictions far outside it.