What is the applicability of the IQ score

Swiss canteen Intelligent people intelligently networked

Originally, IQ was defined as the ratio between intelligence age and actual age, with this ratio being multiplied by 100. A 10-year-old child who performed just as well in an intelligence test as an average 13-year-old child had an IQ of 130. However, this ratio-IQ is only applicable to children - otherwise an 80-year-old would have the same number Solves tasks like an average 20-year-old, only an IQ of 25.

For adults, the IQ is therefore defined by the percentage rank in the population. The IQ is defined as a normally distributed variable with a mean of 100 and a standard deviation that depends on the scale used. The three most common scales are the Changer scale with a standard deviation of 15 that Stanford-Binet scale with standard deviation 16 and the Cattell scale with standard deviation 24.

Depending on the scale used, different IQ values ​​therefore correspond to the same percentile rank.

Deviation from the mean in standard deviations
T value20304050607070.58090100
IQ according to the Wechsler scale557085100115130130.8145160175
Stanford-Binet scale IQ526884100116132132.9148164180
IQ according to the Cattell scale ("English Norm")285276100124148149.3172196220
Percentage rank in the population (percentile)0.132.315.95084.197.798.099.8799.99799.99997

Until 2001, Mensa Switzerland communicated the IQ test results both on the Cattell scale (then known as the "English Norm") and on a Cattell scale, which is no longer used today and shifted down by 16 points, which is known as the "Swiss-German Standard" was designated.

After that, Mensa Schweiz used the Stanford-Binet scale for about a year.Mensa Schweiz has been using the Wechsler scale for the IQ values ​​communicated in the test results since the end of 2002. The values ​​in the upper range are therefore lower today than they used to be, especially lower than on the Cattell scale still used by Mensa England today. Unfortunately, many journalists are not aware of this fact. The alleged child prodigies, who are "almost as clever as Einstein" and who are repeatedly reported in the media, therefore almost always come from England for a reason.

The following can be converted between the Cattell and Wechsler scales:
Cattell IQ = (changer IQ - 100) * 24/15 + 100
Changer IQ = (Cattell IQ - 100) * 15/24 + 100

The blue column with 2.05 standard deviations and percentile 98 indicates the theoretical entry threshold into the cafeteria. On the Wechsler scale, this is an IQ of 130.8. However, we also accept candidates with an IQ of 130 as members, as 130 is the generally accepted threshold for giftedness. A difference of 0.8 points would be smaller than the standard measurement error of an IQ test anyway.