# Ch. 4 stats

 variability provides a quantitative measure of the differences between scores in a distribution and describes the degree to which the scores are spread out or clustered together deviation the distance from the mean population variance equals the mean squared deviation. variance is the average squared distance from the mean standard deviation= standard deviation= √ varience ss or sum of squared is the sum of the squared deviation scores degrees of freedom or df is determined by the number of scores in the sample that are independent and free to vary- defined as df= n-1 unbiased sample statistic if the average value of the statistic is equal to the population parameter biased sample statistic is the average value of the statistic either underestimates or overestimates the corresponding population parameter standard deviation is primarily a descriptive measure: it describes how variable or how spread out the scores are in the distribution Adding a constant to each score (does or does not) change the standard deviation does not multiplying each score by a constant causes the standard deviation to be multiplied by the (same or different) constant same Authormmb65 ID34453 Card SetCh. 4 stats Descriptionch.4 definitions Updated2010-09-13T15:02:58Z Show Answers