Sales data for two years are as follows. Data are aggregated with two months of sales in each "period."

 

MONTHS	SALES	MONTHS	SALES
January—February	107	January—February	113
March—April	102	March—April	110
May—June	145	May—June	154
July—August	171	July—August	174
September—October	118	September—October	119
November—December	98	November—December	104

 

a. Plot the data.

Instructions:

1. Use the line tool (Sales) to draw the sales for each period.

2. To earn full credit for this graph you must plot all required points, beginning with the first unit.

3. To enter exact coordinates, double click on the point and enter the values of x and y.

 

b. Fit a simple linear regression model to the sales data. (Do not round intermediate calculations. Round your answers to 3 decimal places.)

 

 

 

c-1. In addition to the regression model, determine multiplicative seasonal index factors. A full cycle is assumed to be a full year. (Do not round intermediate calculations. Round your answers to 3 decimal places.)
 

 

 

c-2. Fit a regression model to the deseasonalized sales data. (Do not round intermediate calculations. Round your answers to 3 decimal places.)

y=
 

 

 

d. Prepare sales forecasts for next year using both of your regression models derived above to show results both with and without adjustments for seasonality. (Do not round intermediate calculations. Round your answers to 3 decimal places.)


 

 

Sales 200 180 160 140 120- 100 80 TO N_ 6 Foo Period 10 12 14 Sales