When defining the properties of normal distribution we saw that they are perfectly defined when we know their average and standard deviation. In particular we know that:

We can go further in order to calculate the percentage of a population outside of tolerance by simply calculating the z number.

The z number represents: the precise standard deviation from the mean value within the sample tolerance.

Once we know the z number we can calculate the off-tolerance percentage by using the Gaussian table.

Let us take the following example:

Let us calculate z_{min} :

We deduct the percentage of parts outside of tolerance min in the Gaussian table:
_{max} :
We deduct the percentage of parts outside of tolerance min in the Gaussian table:

%HTmin=1.39%

Let us calculate z%HTmin=3.59%

8 Statistical Modules

Trial

€ 0

1 month

Try it for free

Analysis

1 month

All feature's of Ellistat's Analysis Module.

1 user

Technical support and updates included.

Student / Teacher

€ 0

1 year

Checkout

Analysis

1 year

All feature's of Ellistat's Analysis Module.

1 user

Dedicated student licence upon presenting a valud student card.

Technical support and updates included.

Standard

€ 79

per user per month

Checkout

Analysis

Automatic monthly renewal

All feature's of Ellistat's Analysis Module.

Unlimited users.

Technical support and updates included.