...there is much confusion over the actual value, with data and calculations variously yielding 167+, 186, 218, 228, and 230. Extremely high IQ measurement is an inexact science: high IQs are very difficult to quantify because so few people have IQs at that level, giving rise to the problems associated with small sample sizes, ceiling bumping caused by tests not designed to measure such high IQs, and fat tailing which gives the impression more high IQs exist than predicted by a normal distribution. Moreover, there are general disagreements and controversies over the validity of IQ scoring at any level.