DS StatisticsLesson 15Free preview
Stat Variance
This lesson is part of Data Science · All levels
Summary
The variance is the average square of the deviation of each data to the mean, thus being the distribution measure underlying the standard deviation. The unit is the square of the unit of data, for example cmÂ2 when the data is in cm. Calculation of the sample variance divides by n-1 so that estimates of the population are unbiased.
Key points
- Variance = the square of the average difference of each value to the mean.
- The unit of variance is the square of the unit of data (e.g. cm2).
- Standard deviation is the square root of the variance.
- The variance of the population is divisible by n; the variance of the sample is divisible by n - 1.
- The n-1 division (Bessel's correction) gives an unbiased estimate.
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