Standardization and z Scores

compiled by Metty Agustine Primary

What is standard score?

• A standard score can also be known as z score.
• It functions to help researchers understand where an individual score falls in relation to other scores in the distribution.
• A z score is a number that indicates how far above or below the mean a given score in the distribution is in standard deviation units.
• Standardization refers to simply the process of converting individual raw scores in the distribution into standard deviation units.
• Standardized score means the score which “mean” has been standardized.

Why do we need standardization and z score?

• It aims to see whether the individual score has a better performance or not. This can be answered using statistical procedures – standardization and z scores.
• If we have different scale on two scores on different subjects, we need to standardize those into the same scale. (see the example on p. 33 comparing the biology and statistics scores)

To Calculate z Score

To standardize a score, here are the following steps you can use:

1. subtract the mean from an individual score
2. divide it by the standard deviation

Z scores provide researchers a handy way of interpreting where a raw score is in relation to the mean.