by Don McHenry
(Harrisburg, PA USA)
Distribution OF IQ Score
Mr. Terman has distributed IQ scores on the following scales:
50% of IQ scores fall between 90 and 110
70% of IQ scores fall between 85 and 115
95% of IQ scores fall between 70 and 130
99.5% of IQ scores fall between 60 and 140
5% of people have an IQ below 70
If, as you state in your article, "95% of IQ scores fall between 70 and 130", then 5% fall outside the bell curve (gaussian distribution). That would mean that the total 5% is split between the values below 70 (to the left of the curve) and the values above 130 (to the right of the curve). This would obviously be 5% DIVIDED BY TWO, i.e. 2.5%. Which would invalidate the statement "5% of people have an IQ below 70". And, would also invalidate the follow up statement that "There is nothing personal but this 5% population demands special attention.".
As an example: In the attached distribution curve (distributioncurve.jpg) from www.rutherfordiq.com, it actually shows 2.2%@70 and 97.8%@130 respectively.
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