They know this because the people who develop IQ tests know how many people in their norming sample were able to achieve at each level, and they have calculated the scoring to follow a normal curve with a mean of 100 and a standard deviation of 15. An IQ score these days is actually a frequency measure, not an "intelligence quotient" (mental age/chronological age) like it used to be.
What this should mean to people developing an elementary education plan for a child with PG scores is that they almost certainly haven't seen enough children like this to make any judgments about what is or isn't going to work for a particular child.
Last edited by aculady; 08/19/11 11:42 PM.
