Find the first quartile for the set of data.

{7.2, 5.5, 7.1, 8.4, 5.6, 5.1, 9.9}

5.5

7.1

8.4

6.97

To find the first quartile, first arrange the data in ascending order: {5.1, 5.5, 5.6, 7.1, 7.2, 8.4, 9.9}

The formula to find the first quartile is:
Q1 = (n+1)/4
Q1 = (7+1)/4
Q1 = 2

The first quartile is the value at the 2nd position in the ordered data set, which is 5.5.