Z-scores normalisation are a way to compare results from a test to a “normal” population and bring them to a same comparable scale. Advantages of ZScore can thus be:
$$ z\_score = \frac{x-\bar x}{\sigma} $$
The Z score normalisation has the following advantages:
- Z Score can be used to compare raw scores that are taken from different tests
- Z score takes into account both the mean value and the variability in a set of raw scores.
And the Disadvantages of Z score are:
- Z Score always assume a normal distribution.
- If the data is skewed, the distribution of the left and right of the origin line is not equal.