I was looking at an answer for:

Sales (in thousands) of the new Thorton Model 506 convection oven over the eight-week period since its introduction have been as follows: Week Sales 1) 18.6 2) 21.4 3 )25.2 4) 22.4 5 )24.6 6 )19.2 7 )21.7 8) 23.8

a. Which exponential smoothing model provides better forecasts, one using a = .6 or a = .2? Compare them using mean squared error.

b. Using the two forecast models in part (a), what are the forecasts for week 9?

Please show all work no excel please show formulas

but from the response, I cannot determine how they calculated the forecast (see attached). When I add 18.6 and 21.4 I get 40 / 2 = 20. not 20.28

File Home Insert Page Layout Formulas Data Review View Help Tell 6 Cut Calibri 11 V A 29 Wrap Text BB Copy - Paste BIU - - DA- E Format Painter Merge & Center Clipboard Font Alignment J14 X fx alpha=0.2 A D E F G H 1 week - actual value > forecast * error squared error week 2 18.6 3 21.4 18.6 2.8 7.84 W N 4 25.2 20.28 4.92 24.2064 5 4 22.4 23.232 0.832 0.692224 6 5 24.6 22.7328 -1.8672 3.48643584 7 6 19.2 23.85312 4.65312 21.65152573 8 7 21.7 21.061248 -0.63875 0.408004118 9 8 23.8 21.4444992 -2.3555 5.548384019 10 9 22.8577997 63.83297371 9.118996 IN 13 14 alpha=0.6 15 16 17 18 19 20 21 22 23 Sheet1 O Type here to search Eli