DateSaturday 21 August 2004

More statistical syllogisms

Two, plucked randomly from Radio 4 today.

Tory MP on Today insisting that Whitehall produces more paperwork: “the size had gone up 300 per cent, that’s nearly three times…”
No, going up by 300 per cent is four times. In fact it’s confusing – percentages should be avoided generally, and specially if they’re over 100 per cent when it’s an increase.

Later, on a 1pm show, woman talking about IVF treatments: “Everyone has the right to three cycles of IVF treatment, and as each one has a chance of conception of 20 per cent, it would be nice if it could be five….”

Because five times 20 per cent equals 1, right, so you’d be sure to conceive on or before number 5, right? Wrong.
The chance of conceiving in five IVF cycles (assuming each has an independent 20 per cent chance of success) is 67.3 per cent. Because it’s 1 – (0.8^5) [where ^ means “to the power of” – can’t do superscript just now.]

Why A levels really are getting easier

Terrific piece by Jenni Russell in Drilled, not educated at The Guardian (yes, yes, I know, but it’s that good).

A few picks:
In 2000, the Engineering Council delivered a devastating report on the maths skills of students entering maths, science and engineering courses. New students had been given an identical test every year for the preceding decade. As their A-level grades had improved, their mathematical understanding had declined.
The study compared the performance of students who in 1991 had narrowly failed their A-levels with students who had been given a C grade in 1998. The 1991 failures scored higher in the tests than the C-grade students did seven years later.

I find that very scary, as someone who did maths, chemistry, physics, statistics in.. ur.. 1978. Maybe this time I’d understand the degree maths.

Oh, and what a great way to start the article:
We could start by feeling sorry for the schools minister, who is required to talk nonsense in the course of his job. This week David Miliband maintained that there were no credible questions to be asked about the annual rise in A-level passes. He claims that the rise in A grades is purely a matter for celebration; that the quality of the exam remains unchanged, and that anyone who questions this happy picture is simply trying to preserve middle-class educational advantage. On all three counts he is being disingenuous.

A politician being disingenuous, talking nonsense for his job? Perish the thought.

Spam: a retrovirus that infects any online input

Have a look at the output of a Google search for the phrase “George Huff for courtiing ridicule … Against All Odds”. (Go on, I’ll wait.) 218 results as I do it here; I’ve had an attempted spam, which inserts random words into what seems like a theatre reviewing discourse (“although I do have to give props to George Huff for courting ridicule by performing “Against All Odds” (and also saying his favourite film was The Wiz and he identified with Dorothy…bless!).But irony doesn’t only operate along the axis of value. If we give up the idea of “liking things ironically” as we surely should that doesn’t mean our aesthetics are suddenly irony-free. (To claim this would be as silly as all those…”

If anyone knows the original source.. that’d be interesting. (Apart from an Amsterdam-based spammer, of course, who has twisted it and added chemicals into the sentences randomly).

Spam is a retrovirus because people who wouldn’t use it begin to when they think it works. The trouble is that you have to do more of it to make an impact as more people do it. Eventually you kill the host. The comparison with HIV isn’t perfect, but HIV isn’t the only retrovirus.