Question

Ten students compared the amount (in dollars) they spent on books each week. The box plot shows the results. The median amount they spent each week is ____ ($20,$30,$40,$50) . The difference of the first and third quartiles of the data set is ____ ($15,$30,$45,$60).

Answer 1

The median is 50.
The first quartile is 20, the third is 65, the difference is 45.

Answer 2

The box plot contains a box and 5 points:

1. 1st point is the left endpoint (the smallest number);
2. 5th point is the right endpoint (the greatest number);
3. 2nd point is
   `Q_1` - first quartile;
4. 3rd point is
   `Q_2` - second quartile = median;
5. 4th point is
   `Q_3` - third quartile.

Then the median is $50, and
`Q_3-Q_1=\$65-\$20=\$45.`

Answer: $50; $45.