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Lesson 2: Distributions

Standard Normal (z) Distribution

A normal distribution whose mean is zero and standard deviation is 1 is called the standard normal distribution.

Figure 2.13. The Standard Normal (Z) Distribution

Any normal distribution can be converted to a standard normal distribution with simple algebra. This makes calculations much easier.

Calculating in Standard Units

Figure 2.14. Converting a Variable (X) to the Standard Normal (Z)

Calculating Score From Standard Units

Conversely, if you know your score in standard units, you can always work backward to calculate your actual score.

Figure 2.15. Converting the Z-score to a Variable Value (X)

What is the point of using the z-score, you ask? Well, because the z is distributed with mean 0 and a standard deviation of 1, it makes calculations easier. Let’s see how we could have solved the inventory management problem discussed earlier using the z-distribution. 


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