1. Measures of Dispersion CJ 526 Statistical Analysis in Criminal Justice

2. Introduction 1.Variability provides a quantitative measure of the degree to which scores in a distribution are spread out or clustered together

3. Six Measures of Variability 1.Variation Ratio 2.Range 3.Interquartile Range 4.Variance 5.Standard Deviation 6.Coefficient of Variation

4. 2. Range 1.Distance between the largest and smallest scores Not very stable—depends on only two scores

5. 3. Interquartile Range 1.The distance between the first quartile and third quartile The score at the 75 th percentile- the score at the 25 th percentile

6. 4. Variance 1.Mean squared deviation

7. Population and Sample Variance 1.Population - sigma squared -  2 2.Sample - s 2

8. 5. Standard Deviation 1.Square root of variance

9. 6. Coefficient of Variation 1.Used to compare SD’s of variables 2.that have different units of measurement

10. Report Writing - Text Children who viewed the violent cartoon displayed more aggressive responses ( M = 12.45, SD = 3.7) than those who viewed the control cartoon ( M = 4.22, SD = 1.04).

11. SPSS Frequencies Procedure Frequencies –Statistics Central tendency –Mean –Median –Mode

12. SPSS Frequencies Procedure -- continued Dispersion –Standard Deviation –Variance –Range –Minimum –Maximum –Standard Error of the Mean

13. SPSS Descriptives Procedure Descriptives –Minimum –Maximum –Mean –Standard Deviation