Quarterly demand for smartphones at a retailer is as shown. After obtaining initial estimates for level, trend, and seasonal factors, forecast quarterly demand for year 5 using Winter's model with =0.05, =0.1, and . Evaluate the MAD, MAPE, and MSE.

  

3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 A Year 1 2 3 4 B Quarter Period Sales 0 1 I || ||| IV T || ||| IV I =EN-=EN IV IV 2 3 4 5 6 7 8 9 10 11 12 13 14 D 15 16 513 932 1,509 1,902 693 1,163 1,857 2,469 846 1,439 2,271 3,079 1,070 1,751 2,785 3,613 E De-Seasonalized Demand 1,236.50 1,287.88 1,360.25 1,474.63 1,564.63 1,618.25 1,704.50 1,832.50 1,936.75 2,003.75 2,107.00 2,238.00 De-seasonalized Demand Estimiations (using the Regression Line) G Demand/De- Seasonalized Demand Seasonal Estimations Factor H Winter's Model L