appropriate for this series. 9. Use exploratory data analysis to determine whether there is a trend and/or seasonality in mobile home shipments (MHS). The data by quarter are shown in the following table (c2p9): Period Mar-81 Jun-81 Sep-81 Dec-81 Mar-82 Jun-82 Sep-82 Dec-82 Mar-83 Jun-83 Sep-83 Dec-83 Mar-84 Jun-84 Sep-84 MHS 54.9 70.1 65.8 50.2 53.3 67.9 63.1 55.3 63.3 81.5 81.7 69.2 67.8 82.7 79 Period Dec-84 Mar-85 Jun-85 Sep-85 Dec-85 Mar-86 Jun-86 Sep-86 Dec-86 Mar-87 Jun-87 Sep-87 Dec-87 Mar-88 Jun-88 MHS 66.2 62.3 79.3 76.5 65.5 58.1 66.8 63.4 56.1 51.9 62.8 64.7 53.5 47 60.5 Period Sep-88 Dec-88 Mar-89 Jun-89 Sep-89 Dec-89 Mar-90 Jun-90 Sep-90 Dec-90 Mar-91 Jun-91 Sep-91 Dec-91 Mar-92 MHS 59.2 51.6 48.1 55.1 50.3 44.5 43.3 51.7 50.5 42.6 35.4 47.4 47.2 40.9 43 Period Jun-92 Sep-92 Dec-92 Mar-93 Jun-93 Sep-93 Dec-93 Mar-94 Jun-94 Sep-94 Dec-94 Mar-95 Jun-95 Sep-95 Dec-95 MHS 52.8 57 57.6 56.4 64.3 67.1 66.4 69.1 78.7 78.7 77.5 79.2 86.8 87.6 86.4 On the basis of your analysis, do you think there is a significant trend in MHS? Is there seasonality? What forecasting methods might be appropriate for MHS according to the guidelines in Table 2.1 ? TABLE 2.1 A Guide to Selecting an Appropriate Forecasting Method* Quantity of Historical Data (Number of Observations) Forecasting Method Data Pattern Forecast Horizon Naive Stationary 1 or 2 Very short Very short Moving averages Stationary Number equal to the periods in the moving average Exponential smoothing Simple Stationary 5 to 10 Short Adaptive response Stationary 10 to 15 Short Holt's Linear trend 10 to 15 Winters' Trend and seasonality S-curve At least 4 or 5 per season Small, 3 to 10 Short to medium Short to medium Medium to long Bass model Regression-based Trend Short to medium Linear and nonlinear trend with or without seasonality Minimum of 10 with 4 or 5 per season if seasonality is included Causal Can handle nearly all data patterns Minimum of 10 per independent variable Short, medium, and long Time-series Enough to see two peaks and Short, medium, troughs in the cycle and long Can handle trend, seasonal, and cyclical patterns Stationary or transformed to stationary ARIMA Minimum of 50 Short, medium, and long decomposition