Board Thread:General Discussion/@comment-35284508-20181120174212/@comment-35284508-20181124033554

Just to follow on- Random does not mean entirly unpredictable. If we are very sure that there is a 50% return rate on visits in the form of CIs there is still a difference between being confident of seeing that return after 10 visits verses not seeing the return until 100,000 visits. In this study the mean (average) is the 50%. The other factor is called variance and can be seen in the width of the normal curve. It tells us, among other things, how many observations we need to make before we know that the rate has been changed.