Final answer:
The third quartile is the median of the upper half of the scores. If you rank in the 3rd quartile of 1000 students, 750 students rank below you.
Step-by-step explanation:
The third quartile is the median of the upper half of the scores and does not include the median. The upper half also has seven data values; so the median of the upper half will equal the middle value of the upper half, or 60.
Since you are in the third quartile, this means that 75% of the students rank below you. In a dataset of 1000 students, 75% of 1000 is 750. Therefore, there are 750 students who rank below you.