## Seasonal Factors

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# Seasonal Factors

What have you found to be the best way to determine seasonal patterns in data?

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Solution
‎07-08-2014 10:53 AM
Super Contributor
Posts: 340

## Re: Seasonal Factors

Posted in reply to gwcanalytics

I think one statistally right way would be a seasonal Unit-Root-Test:

Proc Arima Data=<Data_Set>;

Identify Var=<Variable> Stationarity=(ADF=(1) DLag=12); /* Augmented Dickey-Fuller-Test with 1 autoregressive term; monthly data */

Identify Var=<Variable> (1) Stationarity=(ADF=(1) DLag=12); /* -"- in 1st differences */

Run;

There are other tests as well (and simpler methods). For example if you have quaterly data and carry out a trend regression you might check the dummy-coefficients for statistical significance.

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Trusted Advisor
Posts: 1,228

## Re: Seasonal Factors

Posted in reply to gwcanalytics

I think we can't generalize which is the best way but as an initial point, data on a graph can give information about seasonal/cyclic patterns.

Solution
‎07-08-2014 10:53 AM
Super Contributor
Posts: 340

## Re: Seasonal Factors

Posted in reply to gwcanalytics

I think one statistally right way would be a seasonal Unit-Root-Test:

Proc Arima Data=<Data_Set>;

Identify Var=<Variable> Stationarity=(ADF=(1) DLag=12); /* Augmented Dickey-Fuller-Test with 1 autoregressive term; monthly data */

Identify Var=<Variable> (1) Stationarity=(ADF=(1) DLag=12); /* -"- in 1st differences */

Run;

There are other tests as well (and simpler methods). For example if you have quaterly data and carry out a trend regression you might check the dummy-coefficients for statistical significance.

Super Contributor
Posts: 340

## Re: Seasonal Factors

Posted in reply to user24feb

P.S.: I guess you are aware that your question is a tricky one. If you ask your question this way, it is almost certain that the respondent puts his/her statistical reputation on the line. :-)

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