Conversion Confidence Calculator
Conversion Confidence Level Calculator
Enter the number of visitors and conversions for each version.
What do the numbers mean?
If Version B is converting better than Version A and the confidence level is 91%, that means that going forward, there is a 91% chance that B will will convert better than A.
PLEASE NOTE:
The confidence level says nothing about the absolute conversion values for Version A and Version B.
In other words, if Version A is currently getting 1.5% conversion and Version B is getting 2.7% conversion, even if the confidence level is 99%, it does NOT mean that you can be 99% confident that B will get a 2.7% conversion rate.
It only means that you have enough data to be 99% confident that B converts better than A.
If you’re looking for a calculator that works the other way around (how long will it take to reach 95% confidence) check out Google’s own duration calculator at:
https://www.google.com/analytics/siteopt/siteopt/help/calculator.html
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July 2nd, 2010 at 10:37 am
How would you use this for A/B testing for PPC ads? Perhaps Conversion = CTR, Visitors = Clicks?
July 2nd, 2010 at 10:40 am
@A
For PPC you would use:
visitors = impressions
conversions = clicks
September 7th, 2010 at 1:55 pm
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November 2nd, 2010 at 3:34 pm
Very nice tool indeed. What assumptions are you making for the variance of the datasets for version A and B. Or are you not using a t-test of some sorts for the confidence level calculation?
We have made our own tool for PPC purposes where each daily day of data is a separate data point and we use a t-test to calculate confidence levels. It works great but is a little cumbersome to use at times and your approach look neat
December 9th, 2010 at 9:42 pm
Fantastic calculator, Ophir.
In many respects, this is better than Google’s Test Duration Calculator as you can see how many visitors will be exposed to a variation based on how much traffic you estimate you’ll recieve.
The only shortcoming is that it doesn’t take into account multiple variations (i.e. if you’re running an MVT test).