Winters' additive model: prediction intervals for forecasts

This macro lets you specify a confidence level other than 95% for the prediction intervals for the forecasts when using Winters' Method additive model is appropriates.

Download the Macro

Be sure that Minitab knows where to find your downloaded macro. Choose Tools > Options > General. Under Macro location browse to the location where you save macro files.

Important

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Required Inputs

  • A column of time series data
  • Seasonal length
  • Level, trend, and seasonal weights
  • Desired number of forecasts
  • Desired confidence level for the prediction intervals

Running the Macro

Suppose the data are in C1, the seasonal length is 2, the level, trend, and seasonal weights are .2 .2 .2 respectively, you want 2 forecasts, and you want 99% prediction intervals stored in the worksheet. To run the macro choose Edit > Command Line Editor and type:
%WINTADD2 C1 2; 
WEIGHT 0.2 0.2 0.2; 
FORECASTS 2; 
CONF 99. 

Click Submit Commands.

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