I’m writing this in early June. It’s always the same. Around about this time, when it gets a little hotter at night, each year I have the same recurring semi-nightmare:
I’m about to go into the exam hall for my maths A level. But I’ve done very little revision. Next to nothing. How will it go? I never get to find out, because I tend to wake up, sweating a little.
This is strange, because I actually like maths, and some 27 years ago, I did OK when I went into that exam hall in real life. But the dream’s had one benefit, at  least. It’s reminded me about a blog I’ve been meaning to write for a while. It does involve maths, yes. And diving too. Wondering how? Do read on.
Have you ever watched a diving competition and wondered what is going on with the scoring system? It’s actually pretty simple. If there are more than three judges, let’s say five, then the scoring system discounts the highest mark and the lowest mark, before working out the total points. And OK, yes, they also factor in the degree of difficulty, but that’s not important for the purposes of my blog, all right?
The point I am making is that this way, the scoring system ignores the residuals or outliers, which may otherwise have skewed the figures.
What’s more important for a fundraiser – the mean or the median?
And this is where fundraising, and indeed my maths A level, comes in. Because fundraisers need to know the difference between the arithmetic mean (or average) and the median when analysing their donor data.  While the mean is essentially the average of all the donations received, the median would be the middle donation, if the donations were listed in ascending order.
The answer is that the median is the more important figure, because your average could well be skewed by a single disproportionate donation, like a legacy or a major donation. You need to take the residuals out or your data will be misleading.
So, if you’re a Trustee reading this, when you’re next presented with budgets by your fundraising manager, ask them to take out the residuals from their analysis. See if it changes things.
And if you’re a fundraiser, think about the way they score diving before plunging into those figures.
This blog was first published by 3rd Sector Mission Control