Question 2.135

2.135 Circular saws

The following table gives the weight (in pounds) and amps for 19 circular saws. Saws with higher amp ratings tend to also be heavier than saws with lower amp ratings. We can quantify this fact using regression.

Weight Amps Weight Amps Weight Amps
11 15 9 10 11 13
12 15 11 15 13 14
11 15 12 15 10 12
11 15 12 14 11 12
12 15 10 10 11 12
11 15 12 13 10 12
13 15
  1. We will use amps as the explanatory variable and weight as the response variable. Give a reason for this choice.
  2. Make a scatterplot of the data. What do you notice about the weight and amp values?
  3. Report the equation of the least-squares regression line along with the value of r2.
  4. Interpret the value of the estimated slope.
  5. How much of an increase in amps would you expect to correspond to a one-pound increase in the weight of a saw, on average, when comparing two saws?
  6. Create a residual plot for the model in part (b). Does the model indicate curvature in the data?