Scatter diagrams and linear regression Quiz

1. $S_{xy}=30$ and $S_{xx}=12$. Find the gradient of the regression line of $y$ on $x$.

• A. $0.4$
• B. $360$
• C. $18$
• D. $2.5$

2. A regression line has $b=3$, with $\bar{x}=4$ and $\bar{y}=20$. Find $a$.

• A. $8$
• B. $32$
• C. $12$
• D. $-8$

3. The line $y=12+2.5x$ was fitted to data with $x$ between 10 and 30. For which value of $x$ is a prediction most reliable?

• A. $x=5$
• B. $x=50$
• C. $x=0$
• D. $x=25$

4. A regression line is $y=4+0.5x$, where $x$ is hours of practice and $y$ is a score. What does 0.5 mean?

• A. The score is 0.5 after no practice
• B. Each extra hour of practice raises the predicted score by 0.5
• C. Each extra point of score needs 0.5 hours
• D. The score rises by 50% per hour

5. The regression line of $y$ on $u$ is $y=10+6u$ where $u=\frac{x-2}{3}$. Find the line of $y$ on $x$.

• A. $y=14+2x$
• B. $y=10+18x$
• C. $y=6+2x$
• D. $y=10+2x$