Monday, 1 October 2012

Season history with seasonality

There's a wonderfully over-used word in statistics, and that's 'maybe'. Only kidding - seasonality. I've heard this mis-applied, never-applied, and over-applied - mostly by me. A Wikipedia definition:

In statistics, many time series exhibit cyclic variation known as seasonalityperiodic variation, or periodic fluctuations. This variation can be either regular or semi regular.

Thanks Wikipedia, not!

The short, and my version: history may often repeat itself.

Why is this important? If you are trying to work out why sales went up at 3am on a given Thursday, ask yourself whether that happens EVERY 3am on a given Wednesday. And then ask why again.  You may have better things to do with your time.

Google Analytics has a fantastic 'compare to past' feature as below. 

You can then see if your acclaimed crazy sales spike was real.

Charts like this are 'probably' showing seasonality. Determining scientifically requires effort or some deeper statistical work. 

How is that helpful? Well, if you do a lot of PR activity and see a sales spike, do you normally see a sales spike at that time? If so, perhaps spend your money more wisely. Give it to me - just like a cornetto.

If you'd like more on this, please do Comment. 

Read this? You can claim a prize. First you have to find me.



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