Week 2
Problem 6-05
Consider the following time series data.
Choose the correct time series plot.
Which Plot?
What type of pattern exists in the data? (Horizontal or Trend Patten?)
Develop a three-week moving average for this time series. Compute MSE and a forecast for week 7. If required, round your answers to two decimal places.
Week Time Series Forecast
Value
1 18
2 13
3 16
4 11 ?
5 17 ?
6 14 ?
MSE: ?
The forecast for week 7: ?
Use α = 0.2 to compute the exponential smoothing values for the time series. Compute MSE and a forecast for week 7. If required, round your answers to two decimal places.
Week Time Series Forecast
Value
1 18
2 13 ?
3 16 ?
4 11 ?
5 17 ?
6 14 ?
MSE: ?
The forecast for week 7: ?
Compare the three-week moving average forecast with the exponential smoothing forecast using α = 0.2. Which appears to provide the better forecast based on MSE? Will it be (Three-week moving average or Exponential smoothing?)
Explain.
The input in the box below will not be graded, but may be reviewed and considered by your instructor.
Use trial and error to find a value of the exponential smoothing coefficient α that results in a smaller MSE than what you calculated for α = 0.2.
Problem 6-21 (Algorithmic)
The Centers for Disease Control and Prevention Office on Smoking and Health (OSH) is the lead federal agency responsible for comprehensive tobacco prevention and control. OSH was established in 1965 to reduce the death and disease caused by tobacco use and exposure to secondhand smoke. One of the many responsibilities of the OSH is to collect data on tobacco use. The following data show the percentage of U.S. adults who were users of tobacco for a recent 11-year period ( http://www.cdc.gov/tobacco/data_statistics/tables/trends/cig_smoking/index.htm ).
|
Year |
Percentage of Adults Who Smoke |
|
1 |
22.9 |
|
2 |
22.1 |
|
3 |
21.6 |
|
4 |
20.9 |
|
5 |
20.9 |
|
6 |
20.4 |
|
7 |
19.5 |
|
8 |
20.4 |
|
9 |
20.4 |
|
10 |
19.6 |
|
11 |
18.9 |
a. Choose the correct time series plot.
|
|
|
|
|
|
(iii) |
|
(iv) |
|
Which plot?
What type of pattern exists in the data? (Positive Linear, Negative Liner, or No Trend?)
b. Use simple linear regression analysis to find the parameters for the line that minimizes MSE for this time series. Do not round your interim computations and round your final answers to three decimal places. For subtractive or negative numbers use a minus sign. (Example: -300) y-intercept, b0 = fill in the blank Slope, b1 = fill in the blank MSE = fill in the blank
c. One of OSH’s goals is to cut the percentage of U.S. adults who were users of tobacco to 12% or less within nine years of the last year of these data. Does your regression model from part (b) suggest that OSH is on target to meet this goal? (yes or no) Use your model from part (b) to estimate the number of years that must pass after these data have been collected before OSH will achieve this goal. Round your answer to the nearest whole number. ? years
1. Problem 6-11
For the Hawkins Company, the monthly percentages of all shipments received on time over the past 12 months are 80, 82, 84, 83, 83, 84, 85, 84, 82, 83, 84, and 83.
a. Choose the correct time series plot.
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|
|
|
Which plot?
b. What type of pattern exists in the data? (Horizontal or Trend Pattern?)
c. Compare a three-month moving average forecast with an exponential smoothing forecast for α = 0.2. Which provides the better forecasts using MSE as the measure of model accuracy? Do not round your interim computations and round your final answers to three decimal places.
|
d. |
Moving average |
Exponential smoothing |
|
MSE |
? |
? |
e. Is it movig average or exponential smoothing?
f. What is the forecast for next month? If required, round your answer to two decimal places. ?
Problem 6-01 (Algorithmic)
Consider the following time series data.
|
Week |
1 |
2 |
3 |
4 |
5 |
6 |
|
Value |
20 |
13 |
16 |
10 |
18 |
14 |
Using the naïve method (most recent value) as the forecast for the next week, compute the following measures of forecast accuracy.
a. Mean absolute error. If required, round your answer to one decimal place.
b. Mean squared error. If required, round your answer to one decimal place.
c. Mean absolute percentage error. If required, round your intermediate calculations and final answer to two decimal places. %
d. What is the forecast for week 7? If required, round your answer to two decimal place.
1. Problem 6-25
Consider the following time series data.
a. Choose the correct time series plot.
Which plot?
What type of pattern exists in the data? (downward trend, upward, or horizontal pattern with seasonality?)
b. Use a multiple regression model with dummy variables as follows to develop an equation to account for seasonal effects in the data. Qtr1 = 1 if Quarter 1, 0 otherwise; Qtr2 = 1 if Quarter 2, 0 otherwise; Qtr3 = 1 if Quarter 3, 0 otherwise. If required, round your answers to three decimal places. For subtractive or negative numbers use a minus sign even if there is a + sign before the blank. (Example: -300) Value = ? + ? Qtr1 + ? Qtr2 + ? Qtr3 + ? t
c. Compute the quarterly forecasts for next year. If required, round your answers to two decimal places. Quarter 1 forecast = ? Quarter 2 forecast = ? Quarter 3 forecast = ? Quarter 4 forecast = ?
Problem 6-23 (Algorithmic)
The medical community unanimously agrees on the health benefits of regular exercise, but are adults listening? During each of the past 15 years, a polling organization has surveyed americans about their exercise habits. In the most recent of these polls, slightly over half of all American adults reported that they exercise for 30 or more minutes at least three times per week. The following data show the percentages of adults who reported that they exercise for 30 or more minutes at least three times per week during each of the 15 years of this study.
|
Year |
Percentage of Adults Who Exercise 30 or more minutes at least three times per week |
|
1 |
41.8 |
|
2 |
45.4 |
|
3 |
47.4 |
|
4 |
45.7 |
|
5 |
46.6 |
|
6 |
44.6 |
|
7 |
47.8 |
|
8 |
51.3 |
|
9 |
49.4 |
|
10 |
49.2 |
|
11 |
49.5 |
|
12 |
52.5 |
|
13 |
50.5 |
|
14 |
55 |
|
15 |
52.5 |
a. Choose the correct time series plot.
Which plot?
Does a linear trend appear to be present? (Possible Positive, Possible Negative, or No Trend?)
b. use simple linear regression to find the parameters for the line that minimizes MSE for this time series. Do not round your interim computations and round your final answers to four decimal places. For subtractive or negative numbers use a minus sign. (Example: -300) y-intercept, b0 = ? Slope, b1 = ? MSE = ?
c. Use the trend equation from part (b) to forecast the percentage of adults next year (year 16 of the study) who will report that they exercise for 30 or more minutes at least three times per week. Do not round your interim computations and round your final answers to four decimal places. For subtractive or negative numbers use a minus sign. (Example: -300) ? %
d. Use the trend equation from part (b) to forecast the percentage of adults three years from now (year 18 of the study) who will report that they exercise for 30 or more minutes at least three times per week. Do not round your interim computations and round your final answers to four decimal places. For subtractive or negative numbers use a minus sign. (Example: -300) ? %
1. Problem 6-19
Consider the following time series.
a. Choose the correct time series plot.
Which plot?
What type of pattern exists in the data? (Horizontal, Downward, or Upward?)
b. Use simple linear regression analysis to find the parameters for the line that minimizes MSE for this time series. Do not round your interim computations and round your final answers to three decimal places. For subtractive or negative numbers use a minus sign. (Example: -300) y-intercept, b0 = ? Slope, b1 = ? MSE = ?
c. What is the forecast for t = 8? If required, round your answer to three decimal places. ?
Problem 6-09
With the gasoline time series data from the given table, show the exponential smoothing forecasts using α = 0.1.
a. Applying the MSE measure of forecast accuracy, would you prefer a smoothing constant of α = 0.1 or α = 0.2 for the gasoline sales time series? Do not round your interim computations and round your final answers to three decimal places.
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b. |
α = 0.1 |
α = 0.2 |
|
MSE |
? |
? |
c. Prefer: ?
d. Are the results the same if you apply MAE as the measure of accuracy? Do not round your interim computations and round your final answers to three decimal places.
|
e. |
α = 0.1 |
α = 0.2 |
|
MAE |
? |
? |
f. Prefer: ?
g. What are the results if MAPE is used? Do not round your interim computations and round your final answers to two decimal places.
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h. |
α = 0.1 |
α = 0.2 |
|
MAPE |
?% |
?% |
i. Prefer: ?