Data Analytics: Foundations to Practice · Descriptive Statistics Fundamentals
Measures of Spread
Two datasets can share an identical average while looking completely different once you account for how spread out their values actually are. This chapter covers the tools that reveal that difference.
Range, the simplest measure of spread, is the difference between a dataset's maximum and minimum values, giving a quick, easily calculated sense of the full span the data covers, though it depends entirely on just two values, the extremes, and says nothing at all about how the remaining values in between are actually distributed.
Key Takeaways
- Range is the difference between maximum and minimum values, a quick but limited measure that ignores everything in between.
- Standard deviation expresses spread in the original unit of measurement, with low values indicating tight clustering and high values indicating wide variation.
- Two datasets can share an identical mean while having dramatically different standard deviations, a distinction the mean alone completely conceals.
- The interquartile range describes the middle 50% of values, deliberately excluding extremes, making it more outlier-resistant than standard deviation.