Learn R: Quartiles, Quantiles, and Interquartile Range

In this course, you will learn how to calculate three important descriptive statistics that describe the spread of the data.

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Key Concepts

Review core concepts you need to learn to master this subject

Quantiles

Quartiles

Quantiles and Groups

Median in Quantiles

Interquartile Range Definition

Interquartile Range and Outliers

Quantiles

Quantiles are the set of values/points that divides the dataset into groups of equal size. For example, in the figure, there are nine values that splits the dataset. Those nine values are quantiles.

Quartiles

Lesson 1 of 3

1
Quartiles
A common way to communicate a high-level overview of a dataset is to find the values that split the data into four groups of equal size. By doing this, we can then say whether a new datapoint fall…
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2
The Second Quartile
We’ll come back to the music dataset in a bit, but let’s first practice on a small dataset. Let’s begin by finding the second quartile (Q2). Q2 happens to be exactly the median . Half of the dat…
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3
Q1 and Q3
Now that we’ve found Q2, we can use that value to help us find Q1 and Q3. Recall our demo dataset: c(-108, 4, 8, 15, 16, 23, 42) In this example, Q2 is 15. To find Q1, we take all of the data poi…
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4
Method Two: Including Q2
You just learned a commonly used method to calculate the quartiles of a dataset. However, there is another method that is equally accepted that results in different values! Note that there is no …
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5
Quartiles in R
We were able to find quartiles manually by looking at the dataset and finding the correct division points. But that gets much harder when the dataset starts to get bigger. Luckily, there is a funct…
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6
Quartiles Review
Great work! You now know how to calculate the quartiles of any dataset by hand and with R. Quartiles are some of the most commonly used descriptive statistics. For example, You might see schools …
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