In a study on speed control, it was found that the main reasons for regulations were to make traffic flow efficient and to minimize the risk of danger. An area that was focused on in the study was the distance required to completely stop a vehicle at various speeds. Use the following table to answer the questions.
MPH Braking distance (feet) 20 20 30 45 40 81 50 133 60 205 80 411
Assume MPH is going to be used to predict stopping distance.
Questions:
1. Which of the two variables is the independent variable? Why?
2. Which is the dependent variable? Why?
3. What type of variable (quantitative: continuous or discrete; qualitative: nominal or rank) is the independent variable?
4. What type of variable is the dependent variable? See above
5. Construct a scatter plot for the data. Label your X and Y axes and show the points.
6. IS there a relationship between the two variables?
7. IS the relationship positive or negative? Why?
8. Suppose the correlation coefficient (r) is 0.966? Does this suggest a strong relationship? Explain
9. What would you conclude about the relationship if r=0? 10. Does correlation mean causation?