MATH 225N: Complete Course Resources

MATH 225N – Week 7 Lab EXAM PRACTICE
QUESTIONS PLUS RATIONALES 2026 |INSTANT
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1. What does the correlation coefficient (r) measure?
A. Strength and direction of a linear relationship
B. The slope of the regression line
C. The y-intercept
D. Causation between variables
Correct answer: A – The correlation coefficient describes both
the strength and direction of a linear relationship.


2. What is the range of possible values for r?
A. 0 to 1
B. –100 to 100
C. –1 to 1
D. –∞ to ∞
Correct answer: C – Correlation values are always between –1
and 1.


3. An r value of –0.85 indicates:
A. Weak positive correlation
B. Strong negative correlation

,C. No correlation
D. Perfect positive correlation
Correct answer: B – Values close to –1 show a strong negative
linear relationship.


4. What does a scatterplot help visualize?
A. Causation
B. Distribution of one variable
C. Relationship between two variables
D. Probability outcomes
Correct answer: C – Scatterplots display how two quantitative
variables relate.


5. A positive slope in a regression line means:
A. As x increases, y decreases
B. x and y are unrelated
C. As x increases, y increases
D. The intercept is positive
Correct answer: C – A positive slope shows y tends to increase
as x increases.


6. What does the slope of a regression line represent?

,A. Average change in y per unit of x
B. Total change in y
C. The correlation coefficient
D. The residual
Correct answer: A – The slope indicates how much y changes for
each one-unit increase in x.


7. What is the y-intercept in a regression equation?
A. The predicted value of y when x = 0
B. The maximum value of y
C. The slope
D. The correlation
Correct answer: A – The y-intercept is where the line crosses the
y-axis.


8. Which equation represents a linear regression model?
A. y = x²
B. y = mx + b
C. y = abˣ
D. y = √x
Correct answer: B – Linear regression follows the form y = mx +
b.

, 9. What is a residual?
A. Observed value minus predicted value
B. Predicted value minus observed value
C. The slope
D. The intercept
Correct answer: A – A residual measures prediction error.


10. A residual of zero means:
A. The prediction was perfect
B. The slope is zero
C. There is no correlation
D. The intercept is incorrect
Correct answer: A – Zero residual means observed equals
predicted.


11. Which graph is best for examining residuals?
A. Histogram
B. Pie chart
C. Residual plot
D. Boxplot
Correct answer: C – Residual plots help assess model fit.


12. A good linear model has residuals that: