The standard deviation (StDev) is the most common measure of dispersion, or how much the data vary relative to the mean. Variation that is random or natural to a process is often referred to as noise.
The standard deviation uses the same units as the data. The symbol σ (sigma) is often used to represent the standard deviation of a population. The letter s is used to represent the standard deviation of a sample.
Use the standard deviation to determine how spread out the data are from the mean.
The standard deviation of the sample data is an estimate of the population standard deviation. Higher values indicate more variation or "noise" in the data. The standard deviation is used to calculate the confidence interval and the p-value. A higher value results in a wider confidence interval and lower statistical power.