# Ch. 4 stats

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1. 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
2. deviation
the distance from the mean
3. population variance
equals the mean squared deviation. variance is the average squared distance from the mean
4. standard deviation=
standard deviation= √ varience
5. ss or sum of squared
is the sum of the squared deviation scores
6. 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
7. unbiased sample statistic
if the average value of the statistic is equal to the population parameter
8. biased sample statistic
is the average value of the statistic either underestimates or overestimates the corresponding population parameter
9. standard deviation is primarily a descriptive measure: it describes
how variable or how spread out the scores are in the distribution
10. Adding a constant to each score (does or does not) change the standard deviation
does not
11. multiplying each score by a constant causes the standard deviation to be multiplied by the (same or different) constant
same
 Author: mmb65 ID: 34453 Card Set: Ch. 4 stats Updated: 2010-09-13 15:02:58 Tags: PSYC402 Folders: Description: ch.4 definitions Show Answers: