Question: what is the standard deviation on an iq test?
Answer: 15 points is one standard deviation for most IQ tests. Nearly 70% of the population score between 85 and 115 – i.e. plus and minus one standard deviation. A very small percentage of the population (about 0.1% or 1 in 1000) have scores less than 55 or greater than 145 – that is, more than 3 standard deviations out!