To determine how many test scores would be at or above the 91st percentile, we need to understand what the 91st percentile means.

The 91st percentile indicates that 91% of the test scores are below a certain value, leaving 9% of the test scores at or above that value. So, we want to find 9% of 800, which represents the number of test scores at or above the 91st percentile.

$9\% \text{ of } 800 = \frac{9}{100} \times 800 = 72$

Thus, 72 test scores would be at or above the 91st percentile.

Would you like more details or have any questions about this?

Here are five related questions to deepen understanding:

1. What is the meaning of a percentile rank in a data set?
2. How would you calculate the 75th percentile for a different sample size?
3. What are quartiles, and how do they relate to percentiles?
4. How can you interpret a score that falls below the 25th percentile?
5. If you know the mean and standard deviation, how can you estimate percentiles using the normal distribution?

Tip: Percentiles are a useful way to compare individual scores to a larger data set, showing where a score ranks relative to others.