Z-Score Normalization (Data Mining)

z score normalization standard deviation

Z-Score Normalization – (Data Mining)

Z-Score helps in the normalization of data. If we normalize the data into a simpler form with the help of z score normalization, then it’s very easy to understand by our brains.

Z- Score Formula

Z-Score formula statistics math

How to calculate Z-Score of the following data?

marks
8
10
15
20  
z score normalization standard deviation
Figure: z score normalization standard deviation

Mean = 13.25

Standard deviation = 4.6

z score normaliation data mining
Figure: z score normalization data mining
marksmarks after z-score normalization
8-1.14
10-0.7
150.3
201.4

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Z Score normalization Excel File Calculations
Figure: Z Score normalization Excel File Calculations

How to calculate Z-Score of the following data?

How do you use a z score table?

1. We can find a specific area under the normal distribution curve.
2. We can find the z-score of the data value and use a Z-Score Table.
Z-Score Table is used to find the area.
A Z-Score Table shows the area percentage to the left of a given z-score on a standard normal distribution.

Advantages of the z score

The z-score is very useful when we are understanding the data. Some of the useful facts are mentioned below;
The z-score is a very useful statistic of the data due to the following facts;
It allows a data administrator to understand the probability of a score occurring within the normal distribution of the data.

The z-score enables a data administrator to compare two different scores that are from different normal distributions of the data.

Is a higher or lower Z score better?

Suppose we have data from two persons. Person A has a high Z score value and person B have low Z Score value. In this case, the higher Z-score indicates that Person A is far away from person B.

What does a negative and a positive z score mean?

A negative z-score indicates that the data point is below the mean.
A positive z-score indicates that the data point is above the mean.

Why is the mean of Z scores is 0?

The standard deviation of the z-scores is always 1 and similarly, the mean of the z-scores is always 1.
Z-scores values above the 0 represent that sample values are above the mean.
z-scores values below the 0 represent that sample values are below the mean.
In the case of squared z-scores, the sum of the squared z-scores is always equal to the number of z-score values.

What is the meaning of the high Z score and low Z score?

  • Suppose we have a  high z-score value then it means a very low probability of data above this z-score.
  • Suppose we have a low z-score value then it means a very low probability of data below this z-score.

Download Important Files of Z Score Normalization

PDF

Slides Presentation

Excel File Calculations

Video Lecture

By:Prof. Fazal Rehman Shamil
CEO @ T4Tutorials
Last Modified: May 25, 2020

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