To calculate the percentile of the data value "25" in the given ordered data set, we can use the following formula:

$\text{Percentile rank} = \left( \frac{L}{N} \right) \times 100$

Where:

• $L$ is the number of data points less than the given value (25).
• $N$ is the total number of data points in the set.

The ordered data is: $8, 9, 10, 11, 12, 13, 16, 18, 21, 25$.

1. Count how many numbers are less than 25. There are 9 numbers less than 25: $8, 9, 10, 11, 12, 13, 16, 18, 21$. So, $L = 9$.

2. The total number of data points $N = 10$ (since there are 10 numbers in total).

Now, apply the formula:

$\text{Percentile rank} = \left( \frac{9}{10} \right) \times 100 = 90$

Thus, the value 25 is located at the 90th percentile.

Would you like more details or have any further questions?

Here are 5 related questions you might find helpful:

1. How do you calculate the percentile rank for other values in the data set?
2. What is the difference between percentile rank and percentage?
3. How would the percentile rank change if the data set was larger?
4. How does the inclusion of duplicate values in the data set affect the percentile calculation?
5. How can percentiles be used in real-life situations, like standardized testing?

Tip: Percentiles are useful for understanding the relative standing of a data point within a data set!