Deciles

College/University

Definition

Refers to a way to split up percentile in a data set—similar to quartiles but rather than dividing up the data into four quarters, it divides it up equally into ten parts. For example, the first decile is the 10th percentile, whereas the third decile is the 30th percentile. Each part will then represent \(1\over10\)th of the population.

Worked examples

\(D_1 = 10\)th percentile\(, \quad D_5 = 50\)th percentile (median)\(, \quad D_9 = 90\)th percentile\(\)

Each decile marks a 10% step through the ordered data set.

\(D_3 = 30\)th percentile\(\)

The third decile means 30% of the data falls at or below that value.

Common mistakes

\(D_1\) is the 1st percentile → \(D_1\) is the 10th percentile The first decile corresponds to the 10th percentile, not the 1st.
There are 11 deciles (\(D_0\) through \(D_{10}\)) → There are 9 deciles (\(D_1\) through \(D_9\)) Deciles divide data into 10 parts using 9 cut points; the endpoints are the min and max.
\(D_6\) is the 6th data value → \(D_6\) is the 60th percentile Deciles mark percentiles, not positions in the raw list.

Where you'll use it next

You'll use deciles when analyzing large data sets in statistics, interpreting standardized test scores, and studying income or wealth distributions in economics and social science.

Found in 1 StudyPug lesson

Understanding Measures of Relative Standing in Statistics

Statistics

Explore z-scores, quartiles, and percentiles to gain powerful insights into data distribution. Learn how to interpret and apply these essential statistical tools for effective analysis.

12th Grade12th