# What does it mean “being normally distributed” [duplicate]

There is an exercise which is used to illustrate how normal distribution works. The exercise starts by saying "Suppose scores on an IQ test are normally distributed..."; What does it mean for the scores to be normally distributed.

Also there is a curve associated to the Normal Distribution, what does this curve tell, what stands on the axis?

An intuitive explanation with a supporting example (optionally), would be much welcomed.

• Wikipedia – nrussell Jul 14 '14 at 13:44
• @nrussell Thanks for the link, but my question is more related to the wording "being normally distributed". How does an IQ score become normally distributed? – Kristof Tak Jul 14 '14 at 14:03
• It's not that it "becomes" normally distributed. You're supposing that the distribution of IQ scores in the population follows a Normal Distribution as on that Wikipedia page. – shadowtalker Jul 14 '14 at 14:12
• Right, as @ssdecontrol says it's not that they are necessarily becoming normally distributed, but rather that the population of IQ data that the sample is drawn from is assumed to follow a Normal Distribution. This means that the sample should exhibit the properties characterized by the probability density function (cumulative distribution function, etc...). There's actually a section of the Wiki specifically devoted to some of these properties. – nrussell Jul 14 '14 at 14:17
• I'd recommend picking up an intermediate probability textbook that explains continuous distributions. – shadowtalker Jul 14 '14 at 14:27