Statistics Definitions > Stanine Score
What is a Stanine Score?
A stanine (“standard nine”) score is a way to scale scores on a nine-point scale. It can be used to convert any test score to a single-digit score. Like z-scores and t-scores, stanines are a way to assign a number to a member of a group, relative to all members in that group. However, while z-scores and t-scores can be expressed with decimals like 1.2 or 3.25, stanines are always positive whole numbers from 0 to 9.
Stanines are also similar to normal distributions. You can think of these scores as a bell curve that has been sliced up into 9 pieces. These pieces are numbered 1 through 9, starting at the left hand section. However, where a standard normal distribution has a mean of 0 and a standard deviation of 1, stanines have a mean of 5 and a standard deviation of 2.
What do Stanines mean?
A person with a score of 9 is in the top 4% of the scorers, while a person with a score of 1 is in the bottom 4%. These types of scores allow you to easily tell if a score is below the mean (a score of 5) or above the mean.
How to Convert a Score to a Stanine
Step 1: Rank the scores from lowest to highest.
Step 2: Assign a stanine score to your scores from Step 1:
|Stanine score||Percentage of scores|
|2||Next bottom 7%|
|3||Next bottom 12%|
|4||Next Bottom 17%|
|6||Next top 17%|
|7||Next top 12%|
|8||Next top 7%|
The mean lies in the middle of the fifth stanine, cutting the center 20% into two parts.
Loss of Information
Stanines are a very simple way of categorizing items into top, middle and bottom percentages. This simplicity means that it’s a very imprecise way to measure anything. Everyone in the same stanine receives the same score. For example, a person at the bottom of the 5th is almost 20 percentage points below the person at the top of the 5th. These differences are what is called “loss of information.”
Stephanie Glen. "Stanine Score: Definition, Examples, How to Convert" From StatisticsHowTo.com: Elementary Statistics for the rest of us! https://www.statisticshowto.com/stanine/
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