Credible interval
The Bayesian counterpart of a confidence interval: a range that contains the true value with a stated probability, given the model and the data.
A 95% credible interval comes from the posterior distribution: given the data and the prior, the true value lies inside it with 95% probability. It reads the way many people wrongly read confidence intervals.
With plenty of data and a weak prior, the two intervals are usually close.
The posterior for the variant's conversion rate puts 95% of its probability between 3.1% and 3.6%.
Related terms
- Confidence intervalA range of values for the true effect that is consistent with the data, at a stated confidence level such as 95%.
- Bayesian A/B testingAnalysing a test by updating a probability model with the data, so results read as probabilities such as the chance a variant beats the control.
- Chance to beat controlThe probability, given the data so far, that a variant's true rate is higher than the control's.