Standard Deviation
Standard deviation is a measure of statistical dispersion that quantifies the variability or spread of a set of data around its mean. It is calculated by the square root of the variance.
Formula:Standard deviation (ฯ) = โ[Variance (Var) = ฮฃ(x - ฮผ)ยฒ / n - 1]
where:* ฯ is the standard deviation* Var is the variance* x is each element in the data set* ฮผ is the mean of the data set* n is the number of elements in the data set
Interpretation:
- Standard deviation measures the degree of variation in a data set.
- A high standard deviation indicates a wide range of values, while a low standard deviation indicates a narrow range of values.
- The standard deviation is an important measure of data dispersion, alongside the range, variance, and coefficient of variation.
Significance:
- Standard deviation is used to:
- Describe the variability of a data set.
- Compare the variability of different data sets.
- Calculate confidence intervals and hypothesis tests.
- Evaluate the performance of statistical models.
Example:
“`Data: [10, 12, 14, 16, 18]
Mean (ฮผ) = (10 + 12 + 14 + 16 + 18) / 5 = 16
Variance (Var) = [(10 – 16)ยฒ + (12 – 16)ยฒ + (14 – 16)ยฒ + (16 – 16)ยฒ + (18 – 16)] / (5 – 1) = 8
Standard Deviation (ฯ) = โ8 = 2.828“`
Therefore, the standard deviation of the data set is 2.828.