To find the median of a data set, you need to follow these steps:

1. Arrange the numbers in ascending order.
2. Identify the middle value.

• If the number of values is odd, the median is the middle value.
• If the number of values is even, the median is the average of the two middle values.

Let's apply this to your data set.

Step 1: Arrange the numbers in ascending order

The data set is: $7, -9, 7, 7, -9, -9, -1$ Arranged in ascending order: $-9, -9, -9, -1, 7, 7, 7$

Step 2: Identify the middle value

Since there are 7 values (an odd number), the median is the middle value, which is the 4th number in this ordered list.

The median is $-1$.

Would you like more details, or do you have any questions?

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Here are 5 related questions to expand your understanding:

1. How does the median change if you add more values to the data set?
2. What is the mode of the data set?
3. What would the median be if all numbers in the data set were increased by 2?
4. How do the mean and median compare when a data set is symmetric?
5. Why is the median a better measure of central tendency in the presence of outliers?

Tip: The median is less affected by outliers and skewed data than the mean, making it a better measure of central tendency in certain cases.