PSYC 218 Chapter 4: Measures of Central Tendency and Variability
Document Summary
Chapter 4 measures of central tenden(cid:272)y and. The arithmetic mean: is defined as the sum of the scores divided by the number of scores. As an equation it can be written as: Properties of the mean: the mean is sensitive to the exact value of all the scores in the distribution. You need to add all scores, so a change in scores = change in the mean: the sum of the deviation about the mean equals zero. Written algebraically, this property becomes (xi - ) = 0. Stated algebraically, (xi - )2 = 0 is a minimum: the mean is very sensitive to extreme scores. This means that if the mean is subtracted from each score, the sum of the differences will equal zero. This happens cause the mean is the balance point of the distribution like a seesaw: the sum of the squared deviation of all the scores about their mean is an minimum.
