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3.8 Time Series HOME  Achievement Objectives  Overview  The Statistics Cycle 
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Decompose data into it's Components
Seasonal Decomposition and Forecasting, Part I (Auckland Uni) Videos  Seasonal Effects  Tourist visitors to NZ from different countries notes, (Merit) The relative influence of each of the components (as a percentage of the overall variation can be investigated. What is the total variation of the Data? (over the time period) What is the Trend Component (% of the total variation of the Data) How do these compare? Discussion MUST be in CONTEXT A good model has not too much residual component Residuals  Are there any unusual observations  do they warrant further investigation. Note: iNZight graphs do not have labels on the vertical axis. For Merit or better you will need to add a lable with units on the vertical axis. O.D.C.A.R.  Obvious (State the obvious)

Exemplar: Decomposing EXEMPLARS:  Alcohol Consumptn: Data csv, Word Worksheet  Google Doc class write up  Travel Destination Data csv  Word Write up  Google Doc class work  Travel Purposes: Data csv 
This analyses the data and separates it into the Trend, Seasonal, & Residuals Smoothed data  Using the Holt  Winters LOWESS technique 
Decomposition animation  Adds seasonal and trend and residual to regenerate the raw data

Discuss relative effect of seasonal effect vs long term trend using numerical values What is the Total Variation of the Data? (over the time period) 13 000 visitors What is the Trend Component (38%)  Less of an influence over total variation than the Seasonal component What is the Seasonal Component (62%)  Cause of most of the variation in the number of visitors from Germany (Remember the context) What is the Residual Component (15%)  This is small indicating that the iNZight Additive model is a reasonably good model for this situation
These calculations are not so flash when the trend line is not linear: Residuals  Are there any unusual observations  do they warrant further investigation.)
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Discuss the decomposed data for these graphs: (tourist numbers to NZ from different countries of origin)
