This note is not really new material for those who work with me, it is one of those examples that I have been dredging out for year after year. But as I've just mentioned the reverend Simpson, and as this blog is holistic, it seems appropriate to head back to the analysis and evaluation of marketing activity.
If programme 1 performs better than programme 2 in a first phase, with a significantly higher response rate, and if programme 1 also performs better than programme 2 in a second phase, - then that does NOT necessarily mean that programme 1 has performed better than programme 2 overall. Even if programme 1 "wins" subsequent phases.
Nothing to do with creative or external factors, just really simple maths. Hence common sense.
But most people seem to understand this better when related to football than to marketing. With my invented numbers:
I just need to recognise, manage and control this effect in real campaigns every single day.