## Sunday, September 27, 2009

### Random Eleven Plus Thoughts

We know that there are real live people who write eleven plus questions. The questions are tested on a sample of children, checked for accuracy, graded, and then dropped into a big bowl. When an authority asks for an eleven plus test, questions have to be answered.

How many questions?
How hard?
How much time?
What percentage pass do you need?

A button is pressed, rather like the National Lottery, and out come the eleven plus questions. The numbers are selected at random – but within certain parameters. Programmers have slaved for weeks, night after night, to be able to respond to variable instructions.

“Select a sample of 50 Mathematics Eleven Plus Questions, at random, from a pool of 250 questions.”

“Construct the test so that 5 difficult, but relevant, questions are selected randomly to fill the final five spots on the paper.”

“Present the other 45 questions randomly – but allow at least one or two easy questions at the beginning of the paper.”

“In the randomisation make sure that there is no bias in the questions towards boys or girls.”

The whole idea of randomisation is to try to make sure that all possible alternatives have an equal chance of being picked. The team who wrote the tests can not pick the questions by numbers because we all know that there is a certain bias towards some numbers. We see this over and over when selecting numbers for the National Lottery.

A randomisation table is used to select numbers. Ideally the table is entered at a random point – like stabbing a finger at the table while looking away. The movement on the table is then selected in a random manner – in other words – by going either up or down or left and right.

A sample block of random numbers could look rather like this:

67 19 01 72 78
03 94 37 34 14
79 56 23 54 91
87 28 57 32 77

This block would be part of a much larger table of random numbers.

All this to say is that the questions on an eleven plus paper do not arrive by chance – but they do arrive randomly.