文档介绍：Time Series and Forecasting
Chapter 16
Goals
Define the components of a time series
Compute moving average
Determinoperates seven amusement parks and five separately gated water parks. Its combined attendance (in thousands) for the last 12 years is given in the following table. A partner asks you to study the trend in attendance. Compute a three-year moving average and a three-year weighted moving average with weights of , , and for successive years.
Weighted Moving Average - Example
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Weighted Moving Average - Example
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Weighed Moving Average – An Example
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Linear Trend
The long term trend of many business series often approximates a straight line
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Linear Trend Plot
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Linear Trend – Using the Least Squares Method
Use the least squares method in Simple Linear Regression (Chapter 13) to find the best linear relationship between 2 variables
Code time (t) and use it as the independent variable
. let t be 1 for the first year, 2 for the second, and so on (if data are annual)
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Year
Sales
($ mil.)
2002
7
2003
10
2004
9
2005
11
2006
13
The sales of Jensen Foods, a small grocery chain located in southwest Texas, since 2002 are:
Linear Trend – Using the Least Squares Method: An Example
Year
t
Sales
($ mil.)
2002
1
7
2003
2
10
2004
3
9
2005
4
11
2006
5
13
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Linear Trend – Using the Least Squares Method: An Example Using Excel
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Nonlinear Trends
A linear trend equation is used when the data are increasing (or decreasing) by equal amounts
A nonlinear trend equation is used when the data are increasing (or decreasing) by increasing amounts over time
When data increase (or decrease) by equal percents or proportions plot will show curvilinear pattern
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Log Trend Equation – Gulf Shores Importers Example
Top graph is plot of the original data
Bottom graph is the log base 10 of the original data which now is linear
(Excel function:
=log(x) or log(x,10)
Using Data Analysis in Excel, generate the l