| A | B |
|---|
| population standard deviation | The square root of the population variance; a measure of the standard distance from the mean. |
| sample variance | The sum of the squared deviations divided by df = n – 1. An unbiased estimate of the population variance. |
| sample standard deviation | The square root of the sample variance |
| degrees of freedom | The number of scores in a sample that are independent and free to vary with no restriction. df = n – 1. |
| biased statistic | A statistic that, on average, consistently tends to overestimate (or underestimate) the corresponding population parameter. |
| unbiased statistic | A statistic that, on average, provides an accurate estimate of the corresponding population parameter. The sample mean and sample variance are unbiased statistics. |
| SS = Σ(X – μ)2 | Formula for a Population |
| SS = Σ(X – M)2 | Formula for a sample |
