In psychology, identification of giftedness is usually based on IQ scores. The arbitrary threshold of IQ = 130 is defined by statistical rarity. By convention, the 5% of scores who fall more than two standard deviations from the mean (or more accurately 1.96) are considered atypical. In the case of intelligence, these 5% are partitioned to both sides of the range of scores, and include the 2.5% who score more than two standard deviations below the mean and the 2.5% who score more than two standard deviations above the mean. Because the average of IQ is 100 and its standard deviation is 15, this rule places the threshold for intellectual disability at IQ = 70, and the symmetrical threshold for giftedness at IQ = 130 (rounded). This arbitrary threshold is used by most psychologists in most countries.