In: Statistics and Probability
The number of cans of soft drinks sold in a machine each week is recorded below
WEEKLY PERIOD |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
SOFT DRINKS SOLD |
122 |
85 |
92 |
98 |
110 |
108 |
115 |
102 |
WEEKLY PERIOD |
9 |
10 |
11 |
12 |
13 |
14 |
15 |
16 |
SOFT DRINKS SOLD |
95 |
98 |
105 |
125 |
85 |
106 |
140 |
84 |
WEEKLY PERIOD |
17 |
18 |
19 |
20 |
21 |
22 |
23 |
24 |
SOFT DRINKS SOLD |
92 |
85 |
78 |
105 |
111 |
152 |
140 |
108 |
A. USING EXCEL, develop forecasts for periods 1 to 24 using a trend line.
B. Calculate the MSE AND MAD
C. CALCULATE and R statistic and interpret it.
PLEASE SHOW WORK IN EXCEL-SNAPSHOT AND EXPLANATION OF METHOD.
THANK YOU!!
SOLUTION:
(a) The trend line equation is Y=a+bx
Using Excel a=INTERCEPT(y values,x values)
b=SLOPE(Y values,X values)
a=3.6714
b=0.0833
The trend line equation is Y=3.6714+0.0833X
forecast values
SUMMARY OUTPUT | ||||||||
Regression Statistics | ||||||||
Multiple R | 0.225695094 | |||||||
R Square | 0.050938276 | |||||||
Adjusted R Square | 0.007799106 | |||||||
Standard Error | 7.043439833 | |||||||
Observations | 24 | |||||||
ANOVA | ||||||||
df | SS | MS | F | Significance F | ||||
Regression | 1 | 58.57901687 | 58.57901687 | 1.18078944 | 0.288958336 | |||
Residual | 22 | 1091.420983 | 49.61004469 | |||||
Total | 23 | 1150 | ||||||
Coefficients | Standard Error | t Stat | P-value | Lower 95% | Upper 95% | Lower 95.0% | Upper 95.0% | |
Intercept | 3.671454219 | 8.250848476 | 0.44497899 | 0.660682239 | -13.43975814 | 20.78266658 | -13.4397581 | 20.78266658 |
X Variable 1 | 0.083386501 | 0.076737831 | 1.086641357 | 0.288958336 | -0.075758019 | 0.242531021 | -0.07575802 | 0.242531021 |
RESIDUAL OUTPUT | ||||||||
Observation | Predicted Y | Residuals | ||||||
1 | 13.84460733 | -12.84460733 | ||||||
2 | 10.75930679 | -8.759306794 | ||||||
3 | 11.3430123 | -8.3430123 | ||||||
4 | 11.84333131 | -7.843331306 | ||||||
5 | 12.84396932 | -7.843969316 | ||||||
6 | 12.67719631 | -6.677196314 | ||||||
7 | 13.26090182 | -6.260901821 | ||||||
8 | 12.17687731 | -4.176877309 | ||||||
9 | 11.5931718 | -2.593171803 | ||||||
10 | 11.84333131 | -1.843331306 | ||||||
11 | 12.42703681 | -1.427036812 | ||||||
12 | 14.09476683 | -2.094766829 | ||||||
13 | 10.75930679 | 2.240693206 | ||||||
14 | 12.51042331 | 1.489576687 | ||||||
15 | 15.34556434 | -0.345564343 | ||||||
16 | 10.67592029 | 5.324079707 | ||||||
17 | 11.3430123 | 5.6569877 | ||||||
18 | 10.75930679 | 7.240693206 | ||||||
19 | 10.17560129 | 8.824398712 | ||||||
20 | 12.42703681 | 7.572963188 | ||||||
21 | 12.92735582 | 8.072644183 | ||||||
22 | 16.34620235 | 5.653797647 | ||||||
23 | 15.34556434 | 7.654435657 | ||||||
24 | 12.67719631 | 11.32280369 |
(b) Calculate MSE and MAD in Excel
period | soft drinks sold(At) | Predicted Y(Ft) | At-Ft | (At-Ft)^2 | |
1 | 122 | 13.84460733 | 108.1553927 | 11697.58896 | |
2 | 85 | 10.75930679 | 74.24069321 | 5511.680528 | |
3 | 92 | 11.3430123 | 80.6569877 | 6505.549665 | |
4 | 98 | 11.84333131 | 86.15666869 | 7422.971561 | |
5 | 110 | 12.84396932 | 97.15603068 | 9439.294298 | |
6 | 108 | 12.67719631 | 95.32280369 | 9086.436902 | |
7 | 115 | 13.26090182 | 101.7390982 | 10350.8441 | |
8 | 102 | 12.17687731 | 89.82312269 | 8068.19337 | |
9 | 95 | 11.5931718 | 83.4068282 | 6956.69899 | |
10 | 98 | 11.84333131 | 86.15666869 | 7422.971561 | |
11 | 105 | 12.42703681 | 92.57296319 | 8569.753513 | |
12 | 125 | 14.09476683 | 110.9052332 | 12299.97074 | |
13 | 85 | 10.75930679 | 74.24069321 | 5511.680528 | |
14 | 106 | 12.51042331 | 93.48957669 | 8740.300949 | |
15 | 140 | 15.34556434 | 124.6544357 | 15538.72833 | |
16 | 84 | 10.67592029 | 73.32407971 | 5376.420665 | |
17 | 92 | 11.3430123 | 80.6569877 | 6505.549665 | |
18 | 85 | 10.75930679 | 74.24069321 | 5511.680528 | |
19 | 78 | 10.17560129 | 67.82439871 | 4600.149061 | |
20 | 105 | 12.42703681 | 92.57296319 | 8569.753513 | |
21 | 111 | 12.92735582 | 98.07264418 | 9618.243537 | |
22 | 152 | 16.34620235 | 135.6537976 | 18401.95282 | |
23 | 140 | 15.34556434 | 124.6544357 | 15538.72833 | |
24 | 108 | 12.67719631 | 95.32280369 | 9086.436902 | |
total | 2541 | 300 | 2241 | 216331.579 |
MSE=
=216331.579/24
=9013.8157
MAD=
=2241/24
=93.375
Therefore MSE is 9013.8157 and MAD is 93.375
(c) R=0.2256
SUMMARY OUTPUT | |
Regression Statistics | |
Multiple R | 0.225695094 |
R Square | 0.050938276 |
Adjusted R Square | 0.007799106 |
Standard Error | 7.043439833 |
Observations | 24 |