PSY30100 Lecture Notes - Lecture 4: Variance, Statistic, Statistical Parameter
Document Summary
Variability measures tell us how much scores differ by or how spread out they are. Central tendencies describe the central point of the distribution and variability describes how the scores are scattered around this central point. Variability can be measured using range or variance. Range is not a robust measure against extreme variables. Standard deviation measures the average distance between a score and the mean. If the mean is not a whole number or is a recurring fraction that cannot be easily subtracted from values, there is an alternative way to find sum of squares. A sample statistic is considered unbiased when the sample average is equal to the population parameter. If the two aren"t equal, the statistics are biased. Sample variance tends to always be slightly smaller than the population variance. Hence in practical cases, sample statistics is calculated over a degree of freedom.
