In: Economics
The following table gives the price (in dollars), weight (in pounds), amps, and maximum cutting depth (in inches) for a collection of 19 circular saws.
Price | Weight | Amps | Depth |
---|---|---|---|
150 |
11 | 15 | 2.4 |
110 | 12 | 15 | 2.2 |
130 | 11 | 15 | 2.4 |
150 | 11 | 15 | 2.3 |
140 | 12 | 15 | 2.4 |
100 | 11 | 15 | 2.4 |
150 | 13 | 15 | 2.5 |
90 | 9 | 10 | 2.5 |
140 | 11 | 15 | 2.4 |
110 | 12 | 15 | 2.4 |
70 | 12 | 14 | 2.4 |
30 | 10 | 10 | 2.5 |
80 | 12 | 13 | 2.4 |
50 | 11 | 13 | 2.4 |
80 | 13 | 14 | 2.4 |
30 | 10 | 12 | 2.5 |
50 | 11 | 12 | 2.5 |
45 | 11 | 12 | 2.5 |
40 | 10 | 12 | 2.4 |
1.Make a prediction about the impact of each independent variable on the dependent variable.
2.Use graphical summaries to examine the relationship between each pair of variables. What do you see? Are there any unusual observations or outliers? Does the data support your predictions?
3.Write the regression equation.
4. Estimate the regression model. Interpret the estimated coefficients.
5. Predict the price of a circular saw that weighs 10 pounds, uses 12 amps of current, and has a maximum cutting depth of 2.5 inches.
6. Describe the fit of the model.
7. Find the residuals for the regression.
8. Test whether or not the coefficients are jointly significant. Be sure to set up the hypothesis, the decision rule, and the conclusion.
9.Test whether or not the price is significantly impacted by amps. Be sure to set up the hypothesis, the decision rule, and the conclusion.
Price | Weight | Amps | Depth | |||||
150 | 11 | 15 | 2.4 | |||||
110 | 12 | 15 | 2.2 | |||||
130 | 11 | 15 | 2.4 | |||||
150 | 11 | 15 | 2.3 | |||||
140 | 12 | 15 | 2.4 | |||||
100 | 11 | 15 | 2.4 | |||||
150 | 13 | 15 | 2.5 | |||||
90 | 9 | 10 | 2.5 | |||||
140 | 11 | 15 | 2.4 | |||||
110 | 12 | 15 | 2.4 | |||||
70 | 12 | 14 | 2.4 | |||||
30 | 10 | 10 | 2.5 | |||||
80 | 12 | 13 | 2.4 | |||||
50 | 11 | 13 | 2.4 | |||||
80 | 13 | 14 | 2.4 | |||||
30 | 10 | 12 | 2.5 | |||||
50 | 11 | 12 | 2.5 | |||||
45 | 11 | 12 | 2.5 | |||||
40 | 10 | 12 | 2.4 | |||||
SUMMARY OUTPUT | ||||||||
Regression Statistics | ||||||||
Multiple R | 0.809847 | |||||||
R Square | 0.655852 | |||||||
Adjusted R Square | 0.587022 | |||||||
Standard Error | 27.83118 | |||||||
Observations | 19 | |||||||
ANOVA | ||||||||
df | SS | MS | F | Significance F | ||||
Regression | 3 | 22141.91 | 7380.637 | 9.528636 | 0.000907 | |||
Residual | 15 | 11618.62 | 774.5744 | |||||
Total | 18 | 33760.53 | ||||||
Coefficients | Standard Error | t Stat | P-value | Lower 95% | Upper 95% | Lower 95.0% | Upper 95.0% | |
Intercept | -303.445 | 304.189 | -0.99756 | 0.334316 | -951.809 | 344.918 | -951.809 | 344.918 |
Weight | -10.808 | 8.721448 | -1.23925 | 0.234294 | -29.3974 | 7.781292 | -29.3974 | 7.781292 |
Amps | 25.674 | 6.13971 | 4.181631 | 0.000802 | 12.58752 | 38.76048 | 12.58752 | 38.76048 |
Depth | 70.02956 | 109.1225 | 0.641752 | 0.53072 | -162.56 | 302.6187 | -162.56 | 302.6187 |
RESIDUAL OUTPUT | ||||||||
Observation | Predicted Price | Residuals | ||||||
1 | 130.8471 | 19.15288 | ||||||
2 | 106.0332 | 3.966826 | ||||||
3 | 130.8471 | -0.84712 | ||||||
4 | 123.8442 | 26.15584 | ||||||
5 | 120.0391 | 19.96091 | ||||||
6 | 130.8471 | -30.8471 | ||||||
7 | 116.234 | 33.76599 | ||||||
8 | 31.09614 | 58.90386 | ||||||
9 | 130.8471 | 9.15288 | ||||||
10 | 120.0391 | -10.0391 | ||||||
11 | 94.36509 | -24.3651 | ||||||
12 | 20.28811 | 9.711894 | ||||||
13 | 68.69109 | 11.30891 | ||||||
14 | 79.49912 | -29.4991 | ||||||
15 | 83.55705 | -3.55705 | ||||||
16 | 71.63611 | -41.6361 | ||||||
17 | 60.82807 | -10.8281 | ||||||
18 | 60.82807 | -15.8281 | ||||||
19 | 64.63315 | -24.6332 |
3. Price = -303.45 - 10.81*Weight + 25.67*Amps + 70.03*Depth
4. Price = -303.45 - 10.81*Weight + 25.67*Amps + 70.03*Depth + u
Interpretation of the estimated coefficients:
As Weight increases by a pound, price of a circular saw decreases by 10.81 dollars, other factors constant.
A unit increase in Amps leads to increase in price of a circular saw by 25.67 dollars, other factors constant.
As Depth increases by an inch, price of a circular saw increases by 70.03 dollars, other factors constant.
5. price of a circular saw that weighs 10 pounds, uses 12 amps of current, and has a maximum cutting depth of 2.5 inches
Price = -303.45 - 10.81*10 + 25.67*12 + 70.03*2.5
= -303.45 - 108.1 + 308.04 + 175.075
= 71.565
=72 dollars
6. R-squared = 0.66
i.e. 68% of the variability around the mean is explained by this model.
7.
Residuals |
19.15288 |
3.966826 |
-0.84712 |
26.15584 |
19.96091 |
-30.8471 |
33.76599 |
58.90386 |
9.15288 |
-10.0391 |
-24.3651 |
9.711894 |
11.30891 |
-29.4991 |
-3.55705 |
-41.6361 |
-10.8281 |
-15.8281 |
-24.6332 Note: max. 4 parts at a time |