Bài giảng Operations Management - Chapter 3: Forecasting

ForecastingMcGraw-Hill/Irwin Copyright © 2012 by The McGraw-Hill Companies, Inc. All rights reserved.You should be able to:List the elements of a good forecastOutline the steps in the forecasting processDescribe at least three qualitative forecasting techniques and the advantages and disadvantages of eachCompare and contrast qualitative and quantitative approaches to forecastingDescribe averaging techniques, trend and seasonal techniques, and regression analysis, and solve typical problemsExplain three measures of forecast accuracyCompare two ways of evaluating and controlling forecastsAssess the major factors and trade-offs to consider when choosing a forecasting technique3-*Student SlidesForecast – a statement about the future value of a variable of interestWe make forecasts about such things as weather, demand, and resource availabilityForecasts are an important element in making informed decisions3-*Student SlidesMAD weights all errors evenlyMSE weights errors according to their squared valuesMAPE weights errors according to relative error3-*Student SlidesForecasts that project patterns identified in recent time-series observationsTime-series - a time-ordered sequence of observations taken at regular time intervalsAssume that future values of the time-series can be estimated from past values of the time-series3-*Student SlidesThese Techniques work best when a series tends to vary about an averageAveraging techniques smooth variations in the dataThey can handle step changes or gradual changes in the level of a seriesTechniquesMoving averageWeighted moving averageExponential smoothing3-*Student SlidesTechnique that averages a number of the most recent actual values in generating a forecast3-*Student SlidesThe most recent values in a time series are given more weight in computing a forecastThe choice of weights, w, is somewhat arbitrary and involves some trial and error3-*Student SlidesA weighted averaging method that is based on the previous forecast plus a percentage of the forecast error3-*Student SlidesA simple data plot can reveal the existence and nature of a trendLinear trend equation3-*Student SlidesSlope and intercept can be estimated from historical data3-*Student SlidesThe trend adjusted forecast consists of two componentsSmoothed errorTrend factor3-*Student SlidesAlpha and beta are smoothing constantsTrend-adjusted exponential smoothing has the ability to respond to changes in trend3-*Student SlidesRegression - a technique for fitting a line to a set of data pointsSimple linear regression - the simplest form of regression that involves a linear relationship between two variablesThe object of simple linear regression is to obtain an equation of a straight line that minimizes the sum of squared vertical deviations from the line (i.e., the least squares criterion)3-*Student SlidesThe better forecasts are, the more able organizations will be to take advantage of future opportunities and reduce potential risksA worthwhile strategy is to work to improve short-term forecastsAccurate up-to-date information can have a significant effect on forecast accuracy:PricesDemandOther important variablesReduce the time horizon forecasts have to coverSharing forecasts or demand data through the supply chain can improve forecast quality3-*Student Slides