Rules of thumb..

Love this story. It shows what happens when you make decisions via algorithms without human oversight or "rule-of-thumb" checks. A man in Liverpool (Liam Thorp) was offered a Covid jab after the NHS algorithm mistakenly took his height to be 6.2 centimeters (rather than 6ft 2ins), it then (correctly) calculated his BMI to be 28,000, i.e. a little on the "fat bastard" (see picture above) side of healthy! Now, we may well have all put on a couple of pounds over lockdown and morbidly obese people are being offered the jab, but this would be ridiculous. 

I increasingly think that it's important for us to realise (and be taught) that algorithms are created by people and people often don't or can't take every permutation and combination of inputs into account when designing them. This is true for simple calculations like this, as well as the most sophisticated AI systems! I've lost count of the number of software errors I've encountered over the years simply through lack of thought to possible input values, i.e. algorithms should be able to handle good input as well protect against bad or erroneous input. The best kinds of systems IMO are combinations of algorithmic computation and symbolic (or rule based) computation, get the algorithm to calculate an answer and then apply a rule-of-thumb to check that it's "sensible".