Here’s a post that appears on my new website, coppelia.io. The problem You’ve been asked to calculate some figure or other (e.g. end of year revenue, average customer lifetime value) based on numbers supplied from various parts of the business. You know how to make the calculation but what bothers you is that some of … Continue reading

A useful property of mixed effects and Bayesian hierarchical models is that lower level estimates are shrunk towards the more stable estimates further up the hierarchy. To use a time honoured example you might be modelling the effect of a new teaching method on performance at the classroom level. Classes of 30 or so students … Continue reading

I remember getting frustrated as an undergraduate trying to find straight answer to this question. The standard text book answer is something like this: “In statistics, the number of degrees of freedom is the number of values in the final calculation of a statistic that are free to vary” That’s from Wikipedia but it’s fairly … Continue reading