(This relates to my programming question on Stack Overflow: Bell Curve Gaussian Algorithm (Python and/or C#)Bell Curve Gaussian Algorithm (Python and/or C#).)
On Answers.com, I found this simple example:
- Find the arithmetic mean (average) => Sum of all values in the set, divided by the numbers of elements in the set
- Find the sum of the squares of all values in the set
- Divide output of (2) over the numbers of elements in the set
- Subtract the square of mean (1) from the output of (3)
- Take the square root of the outcome of (4)
Example: Set A={1,3,4,5,7}
- (1+3+4+5+7)/5 = 4
- (11+33+44+55+7*7)=1+9+16+25+49 = 100
- 100 / 5 = 20
- 20 - 4*4=20-16 = 4
- SQRT(4) = 2
(This comes from a post on wiki.answers.com.)
Now given all that, how can I fit the above data to a bell curve (such as a credit score) ranging from 200 to 800. Obviously the number 5 in the above set would be 500. But then what is the formula for determining what 3 should be on the same scale. Even though the original set Set A={1,3,4,5,7} is not a bell-curve, I want to force it into a bell-curve.
Imagine these are scores of 5 people. Next month the scores might change as follows: Set A2={1,2,4,5,9}
(one guys loses a point, and the top guy gains two more points - the rich get richer and the poor get poorer). Then perhaps a new guy comes into the set: Set A3={1,2,4,5,8,9}
.