How to Calculate Average (Mean)
Add all values together and divide by the count: Mean = Sum ÷ Count. Enter numbers separated by commas, spaces, or new lines for complete statistical analysis.
Example
Dataset: 4, 7, 2, 9, 3
- Mean: (4 + 7 + 2 + 9 + 3) ÷ 5 = 5.0
- Median: Sorted: 2, 3, 4, 7, 9 → middle value = 4
- Mode: No repeated values → no mode
- Range: 9 − 2 = 7
Mean vs Median vs Mode
- Mean (arithmetic average): Sum ÷ count. Sensitive to outliers — one extreme value shifts it significantly
- Median (middle value): The value that splits the dataset in half when sorted. Resistant to outliers. For even-sized datasets, average the two middle values
- Mode (most frequent): The value that appears most often. A dataset can have multiple modes (bimodal, multimodal) or no mode at all
When to Use Each
- Mean: Symmetric data without outliers — test scores, heights, daily temperatures
- Median: Skewed data with outliers — household income, home prices, response times. Median US household income (~$80,000) is far more representative than the mean (~$115,000) because extreme earners skew the average
- Mode: Categorical or discrete data — most popular shoe size, most common survey response, most frequent error code
Standard Deviation
Measures how spread out values are from the mean. A low standard deviation means data is tightly clustered; a high one means data is spread wide.
- 68% of data falls within 1 SD of the mean
- 95% of data falls within 2 SDs of the mean
- 99.7% of data falls within 3 SDs of the mean
This "68-95-99.7 rule" applies to normally distributed data and is used in quality control, grading curves, and scientific research.
Other Types of Averages
- Weighted average: Values are multiplied by weights before summing. Used in GPA calculation (credits × grade points), portfolio returns, and overall course grades
- Geometric mean: The nth root of the product of n values. Used for average growth rates, investment returns, and ratios
- Harmonic mean: Reciprocal of the mean of reciprocals. Used for average speeds and rates