The first quartile is the middle of the lower half of the data.
To find this you must:
1. Order the data from least to greatest.
42, 46, 51, 53, | 66, 70, 70, 90
2. Next, find where the middle of the data set it - see the line above
3. Look at the lower half of the data - see the bold half above.
4. Find the middle of that half - see the underlined numbers above.
5. Find the middle of the 2 numbers
(46 + 51)
2 = 48.5
48.5 is the 1st quartile.
