Statistics
Standard Deviation
A measure of the amount of variation or dispersion in a set of values, calculated as the square root of the variance.
What is Standard Deviation?
The standard deviation quantifies how much individual data points typically deviate from the mean. Unlike variance, it is expressed in the same units as the original data, making it much easier to interpret conceptually.
Why Standard Deviation Matters
It provides a standardized way to evaluate the spread of data and determine whether a specific observation is unusually high or low compared to the rest of the sample.
Example
If the mean resting heart rate of a sample is 70 bpm with a standard deviation of 5 bpm, most participants have heart rates roughly between 65 and 75 bpm.
Common Mistakes
- Assuming that a high standard deviation means the data is error-prone, rather than simply reflecting natural diversity in the population.
- Using standard deviation to summarize the spread of highly skewed data, where percentiles or interquartile ranges are more appropriate.