MLC Board Meeting 45/17/03:

Thus, for example, on an IQ test with a standard deviation of 15, only about .37% of people will score 145 or above. Spread Proportion of Cases + or -1 standard deviation 68.26% + or – 1.5 standard deviations 86.64% + or -2 standard deviations 95.44% + or – 2.5 Standard deviation 98.74 + or -3 standard deviations 99.74% Figure 4-1. ................
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