In: Statistics and Probability
South Shore Construction builds permanent docks and seawalls along the southern shore of Long Island, New York. Although the firm has been in business only five years, revenue has increased from $315,000 in the first year of operation to $1,075,000 in the most recent year. The following data show the quarterly sales revenue in thousands of dollars.
Quarter |
Year 1 |
Year 2 |
Year 3 |
Year 4 |
Year 5 |
|||||
1 |
24 |
40 |
80 |
92 |
163 |
|||||
2 |
97 |
144 |
154 |
197 |
292 |
|||||
3 |
172 |
245 |
329 |
389 |
439 |
|||||
4 |
22 |
23 |
48 |
83 |
181 |
a. Which of the following is the correct time series plot?
What type of pattern exists in the data?
There appears to be a seasonal pattern in the data and perhaps a
b. Use the following dummy variables to develop an estimated regression equation to account for any 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. Round your answers to whole number.
Revenue= _ + _ Qtr1 + _ Qtr2 + _ Qtr3
Compute the quarterly forecasts for next year.
Quarter 1 forecast |
|
Quarter 2 forecast |
|
Quarter 3 forecast |
|
Quarter 4 forecast |
c. Let Period =1 to refer to the observation in quarter 1 of year 1; Period=2 to refer to the observation in quarter 2 of year 1; . . . and Period=20 to refer to the observation in quarter 4 of year . Using the dummy variables defined in part (b) and Period, develop an estimated regression equation to account for seasonal effects and any linear trend in the time series. Based upon the seasonal effects in the data and linear trend, compute the quarterly forecasts for next year. Round your answers to whole number. Enter negative value as negative number.
The regression equation is:
Revenue = _ + _ Qtr1 + _ Qtr2 + _ Qtr3 + _ Period
The quarterly forecasts for next year are as follows:
Quarter 1 forecast |
|
Quarter 2 forecast |
|
Quarter 3 forecast |
|
Quarter 4 forecast |
a)
Seasonal pattern with trend
b)
Year | Sales | Q1 | Q2 | Q3 |
1 | 24 | 1 | 0 | 0 |
1 | 97 | 0 | 1 | 0 |
1 | 172 | 0 | 0 | 1 |
1 | 22 | 0 | 0 | 0 |
2 | 40 | 1 | 0 | 0 |
2 | 144 | 0 | 1 | 0 |
2 | 245 | 0 | 0 | 1 |
2 | 23 | 0 | 0 | 0 |
3 | 80 | 1 | 0 | 0 |
3 | 154 | 0 | 1 | 0 |
3 | 329 | 0 | 0 | 1 |
3 | 48 | 0 | 0 | 0 |
4 | 92 | 1 | 0 | 0 |
4 | 197 | 0 | 1 | 0 |
4 | 389 | 0 | 0 | 1 |
4 | 83 | 0 | 0 | 0 |
5 | 163 | 1 | 0 | 0 |
5 | 292 | 0 | 1 | 0 |
5 | 439 | 0 | 0 | 1 |
5 | 181 | 0 | 0 | 0 |
Excel > Data > Data Analysis > Regression
SUMMARY OUTPUT | ||||||||
Regression Statistics | ||||||||
Multiple R | 0.815126259 | |||||||
R Square | 0.664430817 | |||||||
Adjusted R Square | 0.601511596 | |||||||
Standard Error | 77.97659905 | |||||||
Observations | 20 | |||||||
ANOVA | ||||||||
df | SS | MS | F | Significance F | ||||
Regression | 3 | 192626.6 | 64208.86667 | 10.56006096 | 0.000449538 | |||
Residual | 16 | 97285.6 | 6080.35 | |||||
Total | 19 | 289912.2 | ||||||
Coefficients | Standard Error | t Stat | P-value | Lower 95% | Upper 95% | Lower 95.0% | Upper 95.0% | |
Intercept | 71.4 | 34.87219523 | 2.047476493 | 0.057396533 | -2.525751459 | 145.3257515 | -2.525751459 | 145.3257515 |
Q1 | 8.4 | 49.31673144 | 0.17032759 | 0.866887688 | -96.14680032 | 112.9468003 | -96.14680032 | 112.9468003 |
Q2 | 105.4 | 49.31673144 | 2.137205709 | 0.048367668 | 0.853199678 | 209.9468003 | 0.853199678 | 209.9468003 |
Q3 | 243.4 | 49.31673144 | 4.935444684 | 0.000149101 | 138.8531997 | 347.9468003 | 138.8531997 | 347.9468003 |
Ft = 71+8*Q1+105*Q2+243*Q3
Year 6 | Ft= 71.4+8.4*Q1+105.4*Q2+243.4*Q3 | Q1 | Q2 | Q3 |
Q1 | 79 | 1 | 0 | 0 |
Q2 | 176 | 0 | 1 | 0 |
Q3 | 314 | 0 | 0 | 1 |
Q4 | 71 | 0 | 0 | 0 |
c)
Year | Sales | Q1 | Q2 | Q3 | t |
1 | 24 | 1 | 0 | 0 | 1 |
1 | 97 | 0 | 1 | 0 | 2 |
1 | 172 | 0 | 0 | 1 | 3 |
1 | 22 | 0 | 0 | 0 | 4 |
2 | 40 | 1 | 0 | 0 | 5 |
2 | 144 | 0 | 1 | 0 | 6 |
2 | 245 | 0 | 0 | 1 | 7 |
2 | 23 | 0 | 0 | 0 | 8 |
3 | 80 | 1 | 0 | 0 | 9 |
3 | 154 | 0 | 1 | 0 | 10 |
3 | 329 | 0 | 0 | 1 | 11 |
3 | 48 | 0 | 0 | 0 | 12 |
4 | 92 | 1 | 0 | 0 | 13 |
4 | 197 | 0 | 1 | 0 | 14 |
4 | 389 | 0 | 0 | 1 | 15 |
4 | 83 | 0 | 0 | 0 | 16 |
5 | 163 | 1 | 0 | 0 | 17 |
5 | 292 | 0 | 1 | 0 | 18 |
5 | 439 | 0 | 0 | 1 | 19 |
5 | 181 | 0 | 0 | 0 | 20 |
Ft = -66+43*Q1+128*Q2+255*Q3+11*t
Year 6 | Ft= -66+43*Q1+128*Q2+255*Q3+11*t | Q1 | Q2 | Q3 | t |
Q1 | 208 | 1 | 0 | 0 | 21 |
Q2 | 304 | 0 | 1 | 0 | 22 |
Q3 | 442 | 0 | 0 | 1 | 23 |
Q4 | 198 | 0 | 0 | 0 | 24 |