# PSYCH 2300

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1. Variability
Provides a quantitative measure of the difference between scores in a distribution and describes the degree to which the scores are spread out or clustered together
2. Range
• The distance covered by the scores in a distribution, from the smallest score to the largest.

URL=Xmax and LRL=Xmin
3. Deviation
• The distance from the mean
4. Population Variance
• Equals the mean squared deviation. Variance is the averaged squared distance from the mean
5. Standard Deviation
6. Standard Deviance
7. Sum of Squares
• SS
• Or the sum of the squared deviation scores
8. Definitional Formula for SS

• 1. Find each deviation score
• 2. Square each deviation score
• 3. Add the squared deviations
9. Computational formula of SS
• 1. Square each score and then add the squared values
• 2. Find the sum of the scores
• 3. Then square this total
• 4. Divide by
10. Population Standard Deviation
11. Population Variance
12. SS for sample
• Definitional Formula
• Computational Formula
13. Sample Variance
14. Sample Standard Deviation
15. Degrees of Freedom
• For a sample of n scores, the degrees of freedom, or df, for the sample variance are defined as .
• The degrees of freedom determine the number of scores in the sample that are independent and free to vary.
16. Biased statistic
A sample statistic is biased if the average value of the statistic either underestimates or overestimates the corresponding population parameter
17. Unbiased Statistic
A sample statistic is unbiased if the average value of the statistic is equal to the population parameter,(the average value of the statistic is obtained from all the possible samples for a specific sample size, n)
 Author: xx.chelsii ID: 222231 Card Set: PSYCH 2300 Updated: 2013-06-03 22:19:18 Tags: Chapter Folders: Description: Variability Show Answers: