Probablity &statistics

1. Nov 1, 2007

Analysis

Dear all

For better conceptual understanding purpose i am posting this query

What is the purpose of normal distribution curve?
We are using this curve quality control applications also.
say for component we are machining in cnc machine.
The dimension limit is 25.00/25.025
we are taking sample and measuring the dimensions periodically.

Assume all the samples are taking are accepted one case.
otherwise some of the compnenets not confiming in second case.
How this situation related to normal distribution curve?
And what we are infering from this?

Thanks
Prakash

2. Nov 1, 2007

mathman

The normal distribution usage come from the central limit theorem (one of the basic theorems in probability theory). Roughly the theorem states that if you have something involving a lot of independent errors, the distribution will be normal.

3. Nov 1, 2007

D H

Staff Emeritus
Laziness is another reason. The normal distribution is very well behaved and lends well to analysis. Sometimes it is valid to assume a normal distribution, sometimes not. It is a good idea to verify the validity of a normality assumption. The normality assumption is valid if the true distribution is indistinguishable from normal, and is usually valid if the corresponding normal distribution is conservative compared to the true distribution.

4. Nov 2, 2007