# How do I produce random variables which follow a negatively skewed distribution?

Most distributions such as the exponential and log-Normal distributions are positively skewed with the mode of the distribution occurring for lower values.

The Weibull distribution is negatively skewed and may be generated [http://www.taygeta.com/random/weibull.xml using random variables which are uniform on the interval (0,1).]

The below produces an open ended negatively skewed weibull distribution with parameters, 2 and 20. It has a median of

$$2^{text{-0.05}ln(2)}text{0.05}$$ = 0.95.

which is of form

$$A^{text{-1/B}ln(2)}text{1/B}$$

where A and B are the two parameters of the Weibull distribution. (See [http://www.weibull.com/AccelTestWeb/weibull_distribution.htm here for formulae).]

compute alpha=2. compute beta=20. compute rvw=((-1/alpha)*(ln(1-rv.uniform(0,1))))**(1/beta). exe.