Short Answers (5 points) Give and explain two characteristics of effective sprea
ID: 356732 • Letter: S
Question
Short Answers
(5 points) Give and explain two characteristics of effective spreadsheets.
(5 points) A general rule in hypothesis testing is to reject H0 if p < ?. If p = 0.024, for what significance (?) values would H0 be rejected?
(5 points) Explain the difference between an unbounded problem and an unbounded feasible region. Does one imply the other (both directions)? Explain.
4. (5 points) Explain the purpose of the correlation matrix in multiple linear regression. What do the values represent? What sorts of values would you prefer to see (large, small, positive, negative...)? Explain.
5. (5 points) In regression modeling, what is a reference category? Explain.
Multiple Choice
Be sure to explain your answers to receive full credit. In some cases, there may be more than one correct answer; you must select all correct answers (but no incorrect ones) to receive full credit.
(5 points) Consider the spreadsheet below. If the formula in cell D2 is copied “right” and “down” into cells D3, and E2:E3, what will be the value in cell E3?
a. 17.
b. 23.
c. 4.
d. 9.
e. None of the above/There is not enough information to tell.
(5 points) Consider the scatterplots of residuals versus fitted values below. Which meet(s) linear regression assumptions?
a. Chart A only.
b. Chart B only.
c. Both A and B.
d. None of the above/There is not enough information to tell.
Explanation:
Midterm Exam
Page 3
DS 411 College of Business, SFSU Spring 2009 Theresa M. Roeder
Use the output below to answer questions 8 through 12. The model is trying to predict traffic delays/person for different cities, based on city characteristics: city size (S, M, L, XL), and average highway and arterial speeds. Assume all regression assumptions are met.
Regression Statistics
Multiple R
R Square Adjusted R Square Standard Error Observations
ANOVA
Regression Residual Total
Intercept
HiWay MPH
Arterial MPH
Small -3.589696886 Large 5.009669683 Very Large 3.410579515
0.889127899 0.790548421 0.773657165 6.474064904
68
5 62 67
Coefficients
df
SS
9808.229632 2598.638015 12406.86765
Standard Error
MS
1961.645926 41.91351638
t Stat
F
46.802227
P-value
Significance F
8.81035E-20
Lower 95%
105.7400079 -1.56805829 -3.382006852 -9.492733928 0.804602997 -3.045490811
139.1041107 -1.073471854 -2.0483615
16.69063456
0.247420454
0.667165757 -3.070243787 2.953037124 -1.215594906 2.103615129 2.3814573370.0203282 3.229696038 1.056006347 0.2950629
Upper 95%
172.4682135 -0.578885418 -0.714716188
2.313340156 9.214736368 9.866649841
Lower 95.0%
105.7400079 -1.56805829 -3.382006852 -9.492733928 0.804602997 -3.045490811
Upper 95.0%
172.4682135 -0.578885418 -0.714716188
2.313340156 9.214736368 9.866649841
8.334261358 -4.33865445
1.043E-11 5.379E-05 0.0031727 0.2287478
8. (5 points) Is the regression model and are all variables significant? a. The model and all variables are significant.
b. The model is significant, but no variables are.
c. The model is not significant, but some variables are.
d. The model is not significant, but all variables are.
e. Neither model nor variables is significant.
f. None of the above/There is not enough information to tell.
Explanation:
9. (5 points) What is the regression equation?
a. Delay = 139.1 – 1.1*HiWay – 2.0*Art. – 3.6*Small + 5.0*Large + 3.4*XL b. Delay = 139.1 – 1.1*HiWay – 2.0*Art. + 5.0*Large
c. Delay = – 3.6*Small + 3.4*XL
d. Delay = 139.1 + 5.0*Large + 3.4*XL
e. None of the above/
There is not enough information to tell.
(Questions continued on the next page!)
Midterm Exam
Page 4
Explanation:
DS 411 College of Business, SFSU Spring 2009 Theresa M. Roeder
(The following 3 questions refer to the regression output on the previous page.)
10. (5 points) How useful is this model for predicting traffic delays? a. It can account for 79.1% of the variability in Delay.
b. It can account for 77.4% of the variability in Delay.
c. It can account for 88.9% of the variability in Delay.
d. It can account for 62.6% of the variability in Delay. e. It can account for 60.0% of the variability in Delay. f. None of the above/
There is not enough information to tell.
11. (5 points) Use this model to predict the Delay if the average highway speed is 57MPH, the average arterial speed is 28MPH, and the city is medium-sized.
a. 20.4.
b. 54.
c. 136.
d. 16.4.
e. None of the above/
There is not enough information to tell.
12. (5 points) Another model has been proposed with p = 0.002, R2 = 0.78, and adjusted R2 = 0.75. Below is a table comparing error measures for the two models. Which would you recommend for forecasting purposes?
Model 1.
Model 2.
Either Model 1 or Model 2.
None of the above/
There is not enough information to tell.
Explanation:
Explanation:
Model 1 (above)
ME
0.02
-0.05
MAD
5.9
2.2
MSE
38.2
Explanation:
Midterm Exam
Page 5
Calculations
13. (20 points) In order to plan for an upcoming fish drought, the government of a South Pacific island is trying to build a model to determine the amount of profit that can be made from fishing. The island has a population of 40,000. Each resident eats an average of 0.5 lbs of fish/day. Any excess fish that is brought in can be sold to exporters for $8/lb. Fish costs $1/lb to bring on-land. Currently, there is a monthly supply of 1M lbs of fish. However, the islanders prefer to not fish more than 80% of the available stock. Because the upcoming drought, supply is expected to decrease by 5%/month over the next year. Draw an influence chart to help develop a spreadsheet model for the profit over the next year.
Model 1 (above)
ME
0.02
-0.05
MAD
5.9
2.2
MSE
38.2
Explanation / Answer
1 Hidden unnecessary rows and columns- The unnecessary rows and columns make the spreadsheet look more complex and calculation gets more difficult. The spreadsheet also becomes small and can fit into the computer screen. There should be proper use of consistent color and schemes. In an effective spreadsheet the headings can be colored or made bold to make it identifiable. Otherwise there will not be any difference between headings and contents.
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