IQ levels
This can vary depending on the test. I seem to recall reading somewhere years ago that an IQ of above 30~50 was required to be clinically defined as a human. Below 85 was clinically mentally retarded (remember the film Alien 3 and the ass-kissing character with the nickname 85?). Also I thought genius was defined to be above 180 with a sliding scale going from average - intelligent - very intelligent - gifted - very gifted - genius.

A quick google search seems to indicate that there is no common decision on the matter and it'll just depend on which test and scale you use.
e.g. www.personality-and-aptitude-career-tests.com/wechsler-iq-test-ratings.html

Entry into MENSA requires an IQ in the top 2% of the population, which I think works out as an IQ greater than 148.

/relurk
(Dr_Faustus filius of a femina canis, Wed 10 Feb 2010, 13:06, 1 reply)

Pretty much
The difference to be noted is the standard deviation of the scale you've chosen if you need to compare.

For most IQ tests that a psychologist administers, the SD is 15. So an IQ of 130+ is the top 5%. For most tests that people quote, the SD is 21-23, so an IQ of 140+ is in the top 5%.

This means that most psychologists worth their salt use percentiles to avoid confusion. So you'll usually get a percentile range (eg 75th-84th percentile) which you can then convert to whatever score you "want".

Basic statistics really needs to be covered at school. All I remember is asking people about their favourite ice cream flavour and charting it...
(mmmm curry doesn't really understand this sig lark, Wed 10 Feb 2010, 15:16, closed)