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Why I don't speed (anymore)

Not too long ago I was caught speeding going from Hartfield to East Grinstead. At the time I was furious, and I was even more upset when I read my options in the letter that Sussex Police sent me:

  1. Accept points on my license
  2. Pay for a speed awareness course
I really really did not want points on my license, and so I was facing the £50 odd pounds (don't exactly recall what it cost) to pay for the course. I remember thinking, "What a con! They've turned the whole process into a money-making scheme. First I get fined for the ticket, now I have to pay for a course!" images The closest course to me was at the East Grinstead football club, and I had to take the afternoon off work to attend, which added insult to injury as far as I was concerned. I set off and rather grumpily sat myself down in the chair to tick the box and get it over and done with.

I must say my expectations about the course could not have been more wrong. After about 15 minutes I was riveted. The information presented, the people that ran the course, the exercises we did, it was a really great afternoon. By the time I left I really felt I'd got good value for money and I'd personally highly recommend the course. I jokingly said to my friends at the time that they ought to go and get caught speeding so that they can take the course! I won't give all the details, but there was one moment in particular that really stuck out for me. At the beginning, we'd been asked to write down all the reasons why we sped or felt it was ok to speed. Of course we all came up with things like "I was late", or "I wanted to get there faster", even things like "it's fun!" Right at the end of the course we were given an example of a little girl, her mum was about to take her to school but they'd forgotten something like her PE kit. So the mum went back inside the house for (get this), 30 seconds, when the little girl saw her friend across the road. The girl ran across the road to catch up with her and was hit by a car going 40mph. She died. This was actually made into an advert, you might remember it

Now this car was driven by a man who drove that way to work every day. He cut through a residential area to avoid traffic, and thought nothing of going just 10mph over the speed limit. The thing he did not take into account however, was the statistics involving the speed of the car and the mortality rate of people hit by cars. It's quite staggering, (for mathematical reasons I'll cover in another post), but the difference an extra 10mph makes is enormous.

Now think about this, every year there are around 1500 DEATHS from traffic accidents in the UK. That means, every day, 5 families get a call from a police person telling them that their father, husband, wife, daughter, etc., is not coming home that evening. Just think about the amount of pain and distress that causes, and the fact that it would be slashed in half or more if people simply stuck to the speed limit. We're not even including in that injuries and disablement, which run much higher than that.

One thing people often gripe about is speed cameras, but here's an interesting fact. In East Grinstead there is a speed camera on London Road heading out towards Felbridge. In the years before that was installed, the speed limit was 40mph and there were several road deaths in that period, one of them a school child. So the safety campaigners got it reduced to 30mph, and funnily enough the number of deaths on the road did not change too much, mainly because people were still speeding. Since that camera has been installed, the number of deaths on that road (they said in the course), has fallen to zero. That's right, none.

So my message to those of you that haven't had the fortune to do this course, next time you're trying to save 30 seconds by driving at 40mph or more in a 30-zone, is it really worth risking someone else's life for that? Have some sense of decency, and stick to the speed limit.

(Published on 4 Apr 2016)


Why Sky Sports News is wrong about Cristiano Ronaldo

In this article here- SKY SPORTS

Mr Balague makes a pretty hasty claim that Ronaldo's days as a goal-scoring machine are behind him. In this article we'll take a closer look at that claim and see if it stacks up to mathematical scrutiny. This is an actual piece of maths I did with a student recently in a statistics lesson. Ok, so first of all, let's get the numbers. To simplify matters we'll just look at league goals over his entire career:

Which if you graph looks like this:

Pretty decent. Now we can see that from 2010 up until 2015, he's been pretty consistent in his goal scoring capabilities. Let's take that then to be the mean rate of goals, which works out to roughly 1.164 goals per game. This is a Poisson distribution, with mean rate of 1.164. We take this to be the null hypothesis. The alternative hypothesis then is that the mean is less than that. Let's do a standard 5% tolerance test. Now let's look at the most recent season gone. In this he's played 28 league games, which means if he was scoring at the mean rate that would be roughly 32 goals we would expect. So to test this we would need to establish what the probability is of him scoring a measly 27 goals is when his supposed average is 32. In mathematical language then, what is P(X <= 27) when X~Po(32).

Since the Poisson tables don't go up to 32, we approximate using a Normal distribution N(32, 32). So, to look this up in the tables we must translate it to the standard Normal distribution, so z = (27 - 32 ) / 32 = -0.16 roughly. Looking that up in the Normal tables gives a probability of 56%. But remember the tables only give us the value for the positive side. As in the diagram below we've essentially worked out the probability it is less than +0.16, which is the orange region, but we want the probability it is less than -0.16, which would be the blue region.

Hopefully it's easy to see that they both add up to one, so we must take the result to be 44%. So what have we established? Well according to the null hypothesis, we would have a 44% chance of obtaining the goal scoring record we have seen of Ronaldo this season. This is well outside the very reasonable 5% tolerance band we allowed ourselves. So under these assumptions, we are forced to conclude that we do not have enough evidence to support Mr. Balague's claim that Ronaldo is past his best. I'm quite disappointed to see such a lack of mathematical rigor in our sports analysis. In the future I'd like to see football pundits backing up their wild claims with some sound statistical analysis, rather than (what has now been made clear) is just his opinion and nothing else. With role models like these football pundits, it's no wonder mathematical standards in schools are dropping at such an alarming rate.

(Published on 15 Mar 2016)