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Standard deviation is a statistical measure that describes how spread out values are within a data set. It shows how far individual values typically deviate from the mean.
Standard deviation measures dispersion, or how much a set of numbers stretches away from its average value. It is commonly denoted by the symbol σ.
Two datasets can share the same mean but behave very differently. Standard deviation reveals whether values are tightly grouped or widely scattered.
Population standard deviation is used when every member of a population is measured. It is calculated as the square root of the variance.
Here, xᵢ represents each value, μ is the mean, and N is the total number of values.
In real-world situations, it is often impractical to measure an entire population. Instead, a sample is used to estimate variability.
This corrected formula reduces bias and is the most commonly used estimator of population standard deviation.
Standard deviation is closely related to confidence intervals and margin of error. When applied to sampling results, it is often referred to as the standard error of the mean.
Smaller standard deviation values typically lead to narrower confidence intervals.
Two cities may share the same average temperature, yet one experiences mild seasonal changes while the other faces extreme fluctuations. Standard deviation explains this difference by capturing variability around the mean.
Yes. Because it is derived from squared differences, standard deviation is always non-negative.
Use population SD when all data points are known, and sample SD when estimating from a subset.
Not necessarily. It simply indicates greater variability, which may be expected in certain contexts.
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