Lines of Best Fit and Linear Models: Grade 8 Math Quiz – PDF Download
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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Question 1
Which statement best describes the fit of the line to the plant data?Plant height and days since planting.
APoor fit: the line misses some points
BPoor fit: the points should lie on a curve
CGood fit: every point is exactly on the line
DGood 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?
AThe rental costs $2.50 in total
BEach extra hour costs $2.50
CThe fixed fee is $2.50
DThe skates are rented for 2.5 hours
Question 5
In \(C=2.5h+15\), what does the y-intercept 15 mean?
AThe cost rises $15 each hour
BThe skates are rented for 15 hours
CThe cost is $15 before any hours are added
DThe 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.
ANo, the points curve instead of following a line
BYes, the line passes through two points
CYes, the points mostly go up
DNo, 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!
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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.
