Category: Data & Statistics
Mean = the sum of the values ÷ the number of values.
Median:
For an odd number of values: Median = the middle value.
For an even number of values: Median = the average of the two middle values.
Be sure to order the values first!
Mode = the value that appears most frequently.
Why it matters: The SAT tests you not just on calculations but interpretation: "Which measure of center best represents this data set?" and "How does adding a value change the mean vs. the median?"
Key insight: The mean is sensitive to outliers; the median is resistant. So, for a data set has an extreme value (outlier), the median is usually the better measure of center.
Practice tip: When a problem changes a data set (adds a value, removes a value, or changes one value), recalculate each measure from scratch rather than trying to adjust the previous answer.
Here are a couple of examples:
