Assumes many shapes depending upon the shape, scale, and location parameters.

Effect of Shape parameter B on Weibull distribution:

- If the shape parameter B is 1, it becomes identical to exponential distribution.
- If 2, then Rayleigh distribution.
- If between 3 and 4, then Normal distribution.

http://www.weibull.com/hotwire/issue14/relbasics14.htm (Weibull distribution)

weibull 63.21

Notice that at the time t = a we expect 63.21% of the population to have failed, regardless of the value of b. The estimated failure rate for each individual widget as a function of time is

http://www.mathpages.com/home/kmath122/kmath122.htm