Serving up my thoughts since 2004

Month: May 2008

Google Website Optimizer Video Tutorial

Google Website Optimizer Tutorial
A few months ago a created a Google Website Optimizer Video Tutorial

I really didn’t do much with it, and since then they’ve slightly updated the interface.

The good thing is that it provides a step-by-step guide explaining exactly how to setup a test, as well as some interesting background information and common mistakes to avoid.

If you find it helpful, please let me know.

Check it out Here.


Conversion Confidence Level Calculator

One of the most common questions when setting up an experiment in Google Website Optimizer is how long will the experiment take?

In other words, how long will it take to have “enough” data.

The official Google Website Optimizer docs say:

If one combination emerges as a clear winner, in the future it will exceed the performance of any of the other combinations with a 95% confidence or better.

But what do you do if you want to estimate the experiment length in advance?

Just use my conversion confidence level calculator

Here is a simple example:

Your site gets 2,000 visitors a week.
If you’re doing a simple A/B split with just two versions (original and test A) then each one gets 1,000 visitors a week.

Your current conversion rate is 2% * 1,000 visitors = 20 conversions a week for the original version.
You are hoping to get a 50% improvement for a 3% conversion rate * 1,000 visitors = 30 conversions a week for the test version.

Here’s what it will look like. The fields in yellow are the fields you enter.

The confidence calculator shows an 84% confidence level.
Not bad, but your boss says she wants at least a 95% confidence before declaring a winner.

You’ll see the confidence level for twice the traffic (two weeks worth of data) is 95%.
This means that if you get the same conversion rates and double the traffic, you’ll have a 95% confidence level.

– Ophir

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