## Friday, September 18, 2009

### Eleven Plus Guessing

Some of our children have yet another eleven plus test to do early next week. In one lesson we discussed, once again, the efficacy of guessing. We put forward the following case:

If there are fifty items in the test, with only a right or wrong answer, then it is reasonably simple to work out the odds.

Range of Marks – Probability

0-50 1 in 1
25 – 50 1 in every 2
30 – 50 1 in every 10
35 – 50 1 in every 300
40 – 50 1 in every 84 000
45 – 50 1 in every 500 million.

In the present eleven plus examination children will be expecting to choose between four answers. You will have reminded them to eliminate the two answers that can not be correct. This leaves them with just two answers to choose from. If your child manages to eliminate correctly the two misleading answers – leaving a simply choice between two answers – then you and your child can work out the odds.

To guess correctly one answer there is a reasonable chance that the correct answer will be chosen. If your child has to guess all fifty answers correctly – then there is a very strong probability that some answers will be guessed incorrectly.

Of course if there is one more option – in other words four answers to choose from – then the odds for one answer out of the fifty questions is still 1 chance in 1. The odds of being able to guess the right answer correctly, however, lots of times, climbs sharply.

Try to make your child to feel that it is good to guess when necessary. The last thing you want is to do is to push your child into a corner. Perhaps the words `make an inspired guess’ should be heralded triumphantly by all sets of parents. The words `lucky’ and `inspired’ also have a certain ring.