The arithmetic mean adds the values and divides by their count. The median identifies the middle of the ordered values, using the average of the two central values when the count is even.
A very large or small value can move the mean considerably while leaving the median less affected. That does not make one summary universally better. The choice depends on the question and the distribution being described.
Look at the underlying values or a useful distribution view alongside either summary. Include the count and any relevant grouping. A single measure can be convenient, but the shape of the collection often explains why two reasonable summaries tell different stories.
Picture this situation.
Consider a small collection of file sizes with one large video. The typical item and the average storage per item answer different planning questions.
A second way to look.
A column name can hide an assumption. Check units, missing values, and the counting rule before combining observations that only appear to be alike.
- Identify which summary is being reported.
- Look for unusually large or small values.
- Keep the distribution and count in view.
Follow a related question
Distinguish an amount from a rate.
Energy and power answer different questionsDistinguish model training from inference.
Training and use are different stagesKeep learning
Related background to continue exploring this subject.
NIST: statistical engineering NIST: the International System of Units