# Joint distribution in layman's terms

Can someone please explain to me in layman's terms what a joint distribution is? I do not understand it after seeing a word problem that pertained to joint distributions. Please provide the intuition and avoid mathematical equations.

• For a discrete distribution of a random variable $X$, you can consider $\Pr(X=x)$ for different values of $x$. For a discrete joint distribution of random variables $X$ and $Y$, you can consider $\Pr(X=x \text { and }Y=y)$ for different values of $x$ and $y$. You need something more sophisticated for random variables with continuous distributions, but the intuitive idea is similar – Henry May 7 '17 at 11:05

As a continuous example, IQs are distributed normally with mean 100 and adult male heights are distributed normally with mean about $5' 10''$. The joint distribution is then a distribution over (height, IQ) pairs, so it tells you about the probability of having both a given height and a given IQ, rather than just one or the other. So armed with the joint distribution, I can now ask questions like 'what is the probability that a man off the street has an IQ between 90 and 110 and is between 5'9'' and 5'11' tall.'