The following formula is used to calculate the First Quartile Range for a given number of data points:
\[ Q1 = \frac{n + 1}{4} \]
Where:
The first quartile range, also known as Q1, is a measure of statistical dispersion that represents the value below which 25% of the data points in a data set fall. It is one of the three quartiles that divide a data set into four equal parts. The first quartile is useful for understanding the lower end of the data distribution and is often used in conjunction with the median and third quartile to describe the spread and central tendency of the data.
Let's say you have a data set with 19 data points. To calculate the first quartile range (Q1), you would use the formula:
\[ Q1 = \frac{n + 1}{4} \]
Substituting the values, you get:
\[ Q1 = \frac{19 + 1}{4} = \frac{20}{4} = 5 \]
Therefore, the position of the first quartile in the data set is the 5th data point.
