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115 CFA
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115.020.20.05 Reading 7 - 5. Quartiles, Quintiles, Deciles, and Percentiles

5. Quartiles, Quintiles, Deciles, and Percentiles

f. calculate and interpret quartiles, quintiles, deciles, and percentiles;

Why are there only three quartiles in a data set divided into four even parts? Why are there four quintiles in a data set divided into five equal parts?
The quartiles/quintiles/x-tiles are the lines that go in-between the parts. They divide the data set and represent the median of the two parts.

What is a Quartile?
A quartile has three median lines that divides data in four even parts.

What is a Quintile?
A quintile has four median lines that divides data into five even parts.

What is a Decile?
A decile has nine median lines that dives a data set into ten even parts.

What is a Percentile?
There are ninety-nine percentiles in a data set, dividing the data into 100 even parts. The 50th percentile is the median.

What is the inter-quartile range?
The interquartile range are the values between the first quartile and third quartile lines. E.g. the middle 50% of the data set.


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