Gifted Issues Discussion homepage Forums Identification, Testing & Assessment What are "ratio iq"s

Hey all.... Been looking over Ruf's book and am so confused by the use of ratio iq scores..... Can anyone shed some light??
Hope you are all having a great summer,by the way!!

Ratio IQs were calculated by dividing mental age (as measured by the assessment intrument) by chronological age. Some of the older IQ tests used ratios or modified ratio scales to calculate this "Intelligence Quotient', the original meaning of IQ. Under this method, a 10 year old who functioned mentally like a 14.5 year old would have a 145 IQ.

Modern IQ tests use rarity on the normal distribution curve to calculate scores, with most having a standard deviation of 15 and a mean of 100. With this method, a 145 IQ would mean that only 1 in 1000 people would score that highly on the test.

Scores obtained by one method aren't equivalent to scores obtained by the other method. There are some tables out there that give general conversion ranges.

Yes, but for IQs near 100 the ratio and deviation measures are close. The ratio measure came first, and the deviation measure was calibrated with a standard deviation of 15 or 16 in order to approximate the ratio measure. According to a http://hiqnews.megafoundation.org/Deviation_IQs.html some equivalences are

ratio_IQ deviation_IQ
120 119
130 128
140 136
150 143
160 150

I would like to know if published research confirms or disagrees with these numbers.

I've posted this link before:
http://www.assess.nelson.com/pdf/sb5-asb3.pdf

On pp. 7-8 are some rough equivalencies reported by Dr. Ruf for the SB5 and SB L-M, the latter of which if I'm not mistaken used ratio scores.

It does seem like being 4.5 years ahead at age 10 is possibly in territory justifying radicalish acceleration, and on that basis the numbers might not be so far distant. I'm interested too.