Same Average, Different Spread: What Standard Deviation Hides
Statistics & Probability
Two housing markets can share the same average price and tell very different stories once you look at the spread. Use standard deviation to find where the real difference lies.
Where this idea comes from
Start here — this is the source that inspired this exploration.
Introduction
National housing reports such as UBS's publish an average price change without the spread behind it — two regions can share the same average and still have very different distributions of individual prices. This exploration replaces that aggregated commentary with property-level data you collect yourself, from a property portal or a national statistics office, for two or more comparable regions. Use mean and standard deviation to show what the headline average hides.
Guiding Questions
- Collect actual asking prices for a sample of properties in two regions with similar average prices. What does the standard deviation of each sample tell you that the average alone doesn't?
- Compare your two regions: same mean, different spread. What does the difference mean in practice for a buyer?
- Model prices in one region as roughly Normal. Use it to flag properties that sit unusually far from the mean.
- Which factor in your data set (location, size, age) best explains the spread? Test one with correlation.