
Re: Is there a name for this distribution?
Posted:
Nov 16, 2013 6:48 PM


On Sat, 16 Nov 2013 14:34:56 0800 (PST), Steve <petertwocakes@googlemail.com> wrote:
>I want to program a random distribution in the range 0.0 to 1.0, similar to a normal distribution, but with the centre point shifted to, say, 0.25. >The quality of the randomness isn't crucial, as long as it is shifted. >Given that I can create a random normalish distribution, which is good enough for my purposes, by averaging a few regular Random(0,1), is there a technique to make a shifted version? >
Problem number 1: "similar to normal" is not at all specific enough, especially when you want to assign a small range. Normal has infinite extent to both sides.
If you just want a standard normal with a new location and variance, you could start with standard normal, mean=0.0 and variance= 1.
Then multiple by a number to limit the range; and add a constant to adjust the mean.
If you wanted to confine a normal to [0,1] while preserving the first 3 SD of range, you would take a normal deviate and divide by 9, then add 0.5. Trim or truncate (whichever you arbitrarily decide) whatever draws exceed the range.
If you want a skewed distribution between 0 and1, you might look at the beta.
 Rich Ulrich

