For datasets that have 9 values, we'd have only 9 deciles. But for other datasets that have 10 or more values, we will have 10 deciles, where the 10^th decile is simply the highest number in the distribution.

The 90^th percentile of a dataset is the same as the 9^th decile of the same set. Any values above the 90^th percentile or the 9^th decile will represent the top (1/10)^th of the data values. The 10^th decile (if it exists) represents the maximum of all the data values.

Quartiles, deciles, and percentiles are statistical measures used to rank a dataset into different numbers of buckets. To know how to calculate quartiles, deciles, and percentiles, we'd use slightly different formulas, but each of those accomplishes the following:

• Quartiles divide the dataset into 4 ranks;
• Deciles divide the dataset into 10 ranks; and
• Percentiles divide the dataset into 100 ranks.