Winters

Winters Method: Multiplicative and Additive Models

Data: Canadian Labour Force (in 000's), age 15 and older. Unadjusted. Collected monthly.

A plot of the years 2001-2004 is given on the next page, to emphasize the seasonal variation in the data.

Winters Method in Minitab:

Stat - Time Series - Winters Method

Select Multiplicative. Seasonal Length = 12. Specify the 3 smoothing constants, and tell Minitab we want a forecast 1 month beyond our series (so for Jan. 2005). Under Time option: Calendar as Month Year, and set start value as 1 1982 (both values given in box, with a space between them), increment 1.

The output is on the next page.

Winters' Method for LabForce

Multiplicative Method

Data LabForceLength 276

Smoothing Constants

Alpha (level) 0.2Gamma (trend) 0.2Delta (seasonal) 0.2

Accuracy Measures

MAPE 0.30MAD 43.22MSD 3060.60

Forecasts

Period Forecast Lower UpperJan/2005 16976.0 16870.1 17081.9




Smoothing Constants


Accuracy Measures

MAPE 0.45MAD 66.14MSD 7021.30

Forecasts





Smoothing Constants


Accuracy Measures

MAPE 0.39MAD 56.75MSD 5401.19

Forecasts


To use Winters Method for additive models, we follow the commands as given earlier, but select Additive as the method. Winters' Method for LabForce

Additive Method


Smoothing Constants


Accuracy Measures

MAPE 0.6MAD 84.2MSD 10684.5

Forecasts



Additive Method


Smoothing Constants


Accuracy Measures

MAPE 0.26MAD 37.56MSD 2163.10

Forecasts


Winters

Documents

Transcript of Winters