# Time Series Forecasting Using Excel

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All the time series forecasts we have presented can also be developed with Excel spreadsheets. Exhibit 15.1 shows an Excel spreadsheet set up to compute the exponentially smoothed forecast and adjusted exponentially smoothed forecast for the PM Computer Services example summarized in Table 15.5. Notice that the formula for computing the trend factor in cell D10 is shown on the formula bar on the top of the spreadsheet. The adjusted forecast in column E is computed by typing the formula = C9 +D9 in cell E9 and copying it to cells E10:E20 (using the "Copy" and "Paste" options that appear after clicking the right mouse button).

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##### Exhibit 15.3.

Excel can also be used to develop seasonally adjusted forecasts. Exhibit 15.4 shows an Excel spreadsheet set up to develop the seasonally adjusted forecast for the demand for turkeys at Wishbone Farms. You will notice that the seasonally adjusted forecasts for each quarter are slightly different from the forecasts computed manually (e.g., SF 1 with Excel equals 16.43, whereas SF 1 computed manually equals 16.28). This is due to the rounding done in the manual computations .

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#### Computing the Exponential Smoothing Forecast with Excel QM

##### Exhibit 15.5.

Introduction to Management Science (10th Edition)
ISBN: 0136064361
EAN: 2147483647
Year: 2006
Pages: 358

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