SSCI 3910U Lecture Notes - Lecture 3: Xm Satellite Radio, Normal Distribution, Unimodality
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Although a measure of central tendency is a quick way to get summary information, it is limited because we do not know how the scores are scattered around the center of the distribution (see figure 3. 1 on p. 29) Measures of dispersion = how the scores of a variable are scattered around the center of the distribution. Dispersion = also referring as variability which is the spread or width of the distribution. The range: to get a quick but rough measure of variability, me might find what is known as the range (r, difference between the highest and lowest scores in a distribution. R = h l: the disadvantage of the range is the fact that it is totally dependent on only two score values. As a result, the range usually gives merely a crude index of the dispersion of a distribution: a better measure is called the interquartile range (iqr):
