Distribution of $F^{-1}(U)$

If $U \sim \text{Uniform}(0,1)$ and $F$ is the CDF of a random variable $X$, what is the distribution of $F^{-1}(U)$?

Answer

If $U \sim \text{Uniform}(0,1)$, then

\[ X = F^{-1}(U) \sim F, \]

i.e. $F^{-1}(U)$ has the same distribution as $X$.

Indeed, for any $x$,

\[ P(F^{-1}(U) \leq x) = P(U \leq F(x)) = F(x). \]

Hence, $F^{-1}(U)$ follows the distribution with CDF $F$.

Notes and comments

Comment 1: For intuition, just reverse what you did (mentally) for the x-axis and y-axis in the previous example.

Comment 2: This is the basis of the inverse transform method used to generate random variables from any distribution.

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