Nine out of (every) ten

dentists recommend....

You know how it goes don't you? We are being told something. It's a "statistic" so it "must be true".

I was trying to explain something to someone yesterday. She is convinced that there are more people in hospital who have been vaccinated than who have not been vaccinated. Vaccination therefore "does not work". My attempts to explain that this is not the case did not work - even with nice little diagrams.

I even tried going back to a billboard advertisement I remembered from kittenhood. It said something along the lines of, I think, "eight out of ten dentists recommend..." From memory this was a certain brand of toothpaste - no longer available. Those eight dentists may no longer be with us to recommend it.  

And that of course is the point. There were only eight dentists recommending it in the advertisement.  Did eighty percent of dentists recommend the toothpaste? Of course they didn't. It was simply an advertising trick designed to get people to buy that brand of toothpaste. 

The Senior Cat explained all this to me when I around five or six years of age. It was a lesson in reading comprehension that I have never forgotten. I doubt I am completely immune to advertising but I think I did learn something very useful that day. I do try to "read" advertising and other "news" sources with at least some thought to what might really being said.  I may not always succeed but I try.

I thought of all this yesterday when I was trying to explain what we are actually being told with respect to the Covid numbers. The anti-vaccination person who had rung me just didn't want to know. The set of numbers handed out by the news media suited her far better than the more accurate picture given by the actual mathematics. 

I am not particularly mathematically literate. If I had not been required to do statistics at university then I would almost certainly have forgotten all but the most basic mathematical processes. I would remember those because knitters, particularly knitters who design things, use them all the time.  A couple of months ago I also used a simple statistical test - because I wanted to find out whether the figures given in something were actually out of the ordinary. Apart from that it has been some years since I used any serious statistics for the social sciences.  I am wary of them. I know they can be abused as much as they can be used. 

That is all the more reason why I think we need to do more to help people become mathematically literate. We all need to know the difference between a number and a percentage. Our mental health might well depend on it.