Whatever you may think of the value of IQ tests, it is surely relevant to a conversation about equality that as many as 16 percent of our species have an IQ below 85, while about 2 percent have an IQ above 130. [According to the Guardian, Johnson then asked whether anyone in the audience had a low IQ. To muted laughter he asked: "Over 16% anyone? Put up your hands."]Adam Taylor responded with:
There are many problems with this statement. First, it's a fudging of what IQ measures. IQ testing is designed to show someone's intelligence relative to others. An IQ of 100 is based on the median score, and higher or lower scores are based on their relation to this median score — scores each standard deviation (SD) up or down are defined as 15 IQ points greater or less. What this means is that if you somehow managed to make the everyone with an IQ below 85 leave the U.K., the curve on which IQ is based would shift, and there would be a new 16% of the population with an IQ below 85. All Johnson is really saying which such a statement is that some people score above average on a test, and some people score below average.Adam doesn't know what he is talking about. First of all the 100 in the IQ distribution curve described above is ONLY for those classified at Caucasian. It is not the "median score" for everybody. The median score for those classified as Asian is actually 115. The median score for those classified as African is 85 (let that sink in for a minute). So Adam has the median score part wrong. Onto Standard Deviation. Standard Deviation is determined mathematically: It is the square root of the average of the squared differences of the values from their average value. It is not "15". It is "15" for this data set So again, the SD of 15 discussed in the quote isn't some random number to fit the data, but rather a result of the data and it's averages. For the different Mean IQ levels the standard deviations will change based on the population data. In the case of Caucasians, one standard deviation from their median is 85. Mind you that IQ's below 85 used to be considered mentally challenged. So now that we've corrected Adam on what the Standard deviation is lets get to his really flawed argument.
What this means is that if you somehow managed to make the everyone with an IQ below 85 leave the U.K., the curve on which IQ is based would shift, and there would be a new 16% of the population with an IQ below 85.Well no. If all the sub 85 IQ people left the researched median would STILL be 100. The base (median) wouldn't change because that number is based on long term research. But per chance we were to run with Adam's assertion that magically the curve would change then if anything, by knocking out all the sub 85 scores, the median IQ score for Caucasians would increase. It would approach that of Asians. Once that happened, one standard deviation down would be around 100. 85 would be at least 2 SD down and represent a very small number of the population. Much smaller than the population in the original setting. people who commit these crimes have low IQ's. But the sheer math? Boris has it right. Adam has it wrong.