[senco-forum] RE: 4th percentile

The best explanations are always the simplest and the one offered by Brendan hits the spot accurately.

It is the concept of Reading Age that is most widely misunderstood and misused in schools.  If a boy has a chronological age of exactly 10 and a reading-age of exactly 8  that does not mean that the boy has a reading deficit of two years.   It means that the boy  has a reading-age deficit of two years if compared with an average child who has an IQ of 100 and only six or seven percent of children have an !Q of 100 

 If the boy is compared with another group of children with the same IQ as himself, he could even have a reading-age surpluss. If compared with yet another group with an IQ of say 120, he would have about a five year deficit.

The concept of 'average' is critical in all standardised data and 'average' is a numerical concept - not human one.  Children may have average heights and weights  but there are no 'average' children.

Eddie C.