Bias and Variability Simulation


David M. Lane


Characteristics of Estimators

The mean is an unbiased estimate of the population mean regardless of the shape of the population distribution. The median is an unbiased estimate for normal distributions but not for skewed distributions. When the formula with N in the denominator is used to estimate variance, the mean of the sampling distribution is less than the population variance and is therefore a biased estimate. The mean has less sample variability than the median for most distributions including those with relatively large skew. However, there are some extreme distributions for which the median has less sample variability.

Please answer the questions:
correct feedback