Found Two great posts today:

User Experience By The Numbers

It seems obvious but really insightful that analytics tell us what is happening, not why - giving us data which can back up or be verified by user testing to complete the picture and answer the 'why' so informed solutions can be suggested.

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Intro to A/B Testing

How to increase site performance through A/B split testing (via @UXBooth)

Lovely overview on A/B testing and how to get started.

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Tools and sites i've been checking on for a while...

www.abtests.com

Share your A/B testing results and learn from others.

www.performable.com

Test layouts, copy and content using templates without the hassle of google analytics and time consuming A/B testing.

 

Dying to try some A/B testing and definatly going to look closer at web analytics in the future, combined with personas.