PSY201H1 Chapter Notes - Chapter 4: Variance, Statistic, Statistical Parameter
Document Summary
Biased statistic - sample variability tends to underestimate the variability in the corresponding population. To correct the biased statistic, we adjusted the formula for sample variance by dividing by n-1 instead of dividing by n. The result of the adjustment is that sample variance provides a much more accurate representation of the population variance. Unbiased statistic - dividing by n - 1 produces a sample variance that provides an unbiased estimate of the corresponding population variance. This does not mean that each individual sample variance will be exactly equal to its population variance. Some variances will overestimate the population value and some will underestimate it. However, the average of all the sample variances will produce an accurate estimate of the population variance. A sample statistic is unbiased if the average value of the statistic is equal to the population parameter. (the average value of the statistic is obtained from all the possible samples for a specific sample size, n)
