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Originally posted by flyingbuttflygrl
We are an emotional species
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Deviations from a Bell-Curve
IQs near the center of the range, between about 75 and 125 are well-represented by a bell curve like the one shown below. However, IQs below about 75 don't fit a bell curve well at all. The reason is that there are some individuals who suffer brain damage and who increase the pool of the seriously retarded. Similarly, it was discovered in 1921, when 250,000 California schoolchildren were screened with IQ tests to determine whether they should be included in the Terman Study of gifted children, that there are a lot more very high IQ score than would be predicted by the bell-curve. For example, the Terman Study found 77 children with IQs of 170 or above, where they would only have expected to find 1 or 2. They found 26 children with IQs of 180, where theory would have predicted only one child with an IQ above 180 in 3,000,000 children. They found one child with an IQ of 201, where the bell-curve predicts only one such child out of every 5,000,000,000 children. Part of this is thought to be a result of uneven rates of mental growth. Some children experience temporary spurts of mental growth that are later offset by temporary slackening of mental development--like children that physically-mature relatively early. Part of it is also a function of the fact that, if there are 4 or 5 children with IQs in the mid-190's (because of "growth spurts"), one of them may have an especially good day and score 5 or 6 points higher than he would normally score, while another of them on that same day might score 5 or 6 points lower than she would usually score. The one that scores higher is the one that catches our attention.
Deviation IQs
Because of these effects, beginning around 1960, psychometrists defined adult scores in terms of percentiles, and then translated those percentiles into the IQ scores that the bell-curve predicts. These percentile-derived scores are called "deviation IQs", and the older (mental age)/(chronological age) IQs are called "ratio IQs". (For a more-complete description of deviation IQs versus ratio IQs, click here.This had the effect of reducing IQ scores, since ratio IQs tend to run quite a bit higher at the higher levels than do deviation IQs. (The highest probably deviation IQ is about 200, since a deviation IQ of 200 would be expected, as mentioned above, to occur only once in every 5,000,000,000 people--the approximate current population of the earth.) The scale shown below the plot presents one approach--(a log-normal conversion)--to estimating the ratio IQs that correspond to given deviation IQs.
The figure below shows the upper half of the "bell-curve" distribution (Gaussian normal distribution) of human intelligence. As the plot shows, 50% of the population has below-average intelligence. As the bell-curve below indicates, 1 person in 10 has an IQ of 120 or above, 1 in 20 boasts an IQ of 126 or above, 1 in 50 is Mensa level, with an IQ of 132 or above, 1 in 100 possesses an IQ of 137 or above, 1 in 1,100 is characterized by an IQ of 150 or above, 1 in 11,000 sports an IQ of 160 or above, 1 in 1,000,000 owns an IQ of 176 or above, and so forth.
For all of you think that you are special or smart because your iq is over say 140... get ready for a wake up call. There are many more "smart" people out there then indicated by the bell cure.
Originally posted by Alexander Tau
For all of you think that you are special or smart because your iq is over say 140... get ready for a wake up call. There are many more "smart" people out there then indicated by the bell cure.
Why exactly did you feel the need to say this?
Originally posted by beyondSciFi
. If IQ was the only indicator of overall intelligence then I would only consider people the 190+ range as truly gifted or geniuses.