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The three dividing points (or quantiles) that split data into four equally sized groups are called quartiles. For example, in the figure, the three dividing points Q1, Q2, Q3 are quartiles.

Lesson 1 of 3
  1. 1
    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…
  2. 2
    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…
  3. 3
    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…
  4. 4
    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 …
  5. 5
    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…
  6. 6
    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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