Question

The data in the table below (and available online) represent monthly gross sales for Ska Brewing Company from 2009 to 2012.  This is real data, let’s help Ska forecast 2013…

Year	January	February	March	April	May	June	July	August	September	October	November	December	Total
9 9	$193,481	$170,674	$228,095	$232,372	$288,188	$304,763	$337,825	$342,121	$320,011	$304,756	$221,514	$235,591
10	$267,782	$225,592	$356,604	$274,723	$377,369	$439,907	$430,999	$485,822	$407,577	$450,234	$315,238	$345,135
11	$319,313	$323,726	$342,353	$361,315	$612,500	$564,599	$518,422	$623,860	$412,091	$530,636	$313,034	$395,686
12	$375,117	$391,677	$426,746	$535,876	$659,204	$582,670	$663,534	$564,901	$636,399	$727,822	$539,011	$450,188
13
Slope

a)Sum up the totals for each year and fill in the blanks above.

b)Forecast demand for each month and the total for 2013 using linear regression.  

c)Graph the data, including the forecasts from part b)in chronological orderto display the seasonal pattern.  Printthis out and attach it.

d)Determine the slope for each month and fill in the blanks above.  According to the slopes, which twomonths are growing the fastest (at about the same rate)?

e) Interpret i) the slope for the two fastest growing month(s) and ii) the annual slope.

Predict the twelve months of 2013 using all data at once with the new =forecast.ets() function in Excel.

Answer 1