Figure 15.21 on the next page gives the Minitab output of using multiplicative Winters€™ method in month 168 to forecast the monthly hotel room averages in months 169 through 180. Here we have used Minitab€™s default option that sets each of the smoothing constants alpha, gamma, and delta equal to .2. Use the Minitab output to find and report the point prediction of and a 95 percent prediction interval for the monthly hotel room average in period 169.

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Minitab Output of Using Winters' Method to Forecast the Monthly Hotel Room Averages FIGURE 15.21 Winters' Method Plot for Room Averages Multiplicative Method 1300 Variable 1200 Actual Fits 1100 Forecasts 95.0% PI 1000 900 Smoothing Constants Alpha (level) Gamma (trend) 800 0.2 0.2 700 - 0.2 Delta (seasonal) 600 500 Accuracy Measures MAPE 2.002 400 MAD 14.324 72 108 126 90 18 162 180 MSD 333.986 36 54 144 Time Period Period Forecast Lower Forecast Lower Upper 845.13 790.20 Upper 1198.27 1229.68 175 169 170 810.04 754.55 772.31 874.62 774.95 718.91 1158.99 1189.52 1119.72 1149.37 176 171 172 736.06 837.69 808.57 911.55 905.28 177 178 917.33 912.83 876.25 870.78 958.41 954.88 173 867.63 829.97 179 787.09 744.04 830.15 992.02 174 953.58 1030.47 180 887.66 843.56 931.75 Room Averages