Quartiles

Definition

Quartiles are values that divide a data set into four equal parts, each containing 25% of the data. They are crucial for understanding the spread and center of a data distribution.

5 Must Know Facts For Your Next Test

1. The first quartile (Q1) is the median of the lower half of the dataset, excluding the median if the number of observations is odd.
2. The second quartile (Q2) is also known as the median of the entire dataset.
3. The third quartile (Q3) is the median of the upper half of the dataset, excluding the median if there are an odd number of observations.
4. Interquartile Range (IQR), calculated as Q3 - Q1, measures statistical dispersion and identifies outliers.
5. Quartiles are used in box plots to visually display data distribution and identify potential outliers.

Review Questions

• What does Q2 represent in a dataset?
• How do you calculate Interquartile Range (IQR)?
• Why might quartiles be useful when analyzing data?

Related terms

Median:

The value separating the higher half from the lower half of a data sample; also known as Q2.

Box Plot:

A graphical representation of data that shows its five-number summary: minimum, Q1, median (Q2), Q3, and maximum.

Percentiles:

$Values$ that divide a dataset into $100$ equal parts. The $25th$, $50th$, and $75th$ percentiles correspond to Q1, Q2, and Q3 respectively.