I.
Notes for Stats (112806)
II. Intro to Correlations
III.
IV.Correlation – trying to find out the relationship between two variable (Are they related?
How much?
In
what way?)
A. Regression – can we make predictions from two correlated variables (using X to predict Y)
B.
r
= ∑(Z
x
* Z
y
)/(n – 1)
i.
Z
x
= (x – X)/s
x
ii. Gives us the degree (direction) and extent (magnitude) of a linear
relationship
V. Covariance – an unstandardized
measures of the relationship between two variables
A. Different from correlation in that we have no range
B. The measures have not been standardized with each other (converted to z scores)
C. C
xy
= ∑(x – X)(y – Y)/(N – 1)
i.
Similar to ∑(x – X)
2
/(N – 1), which you would use if you wanted to get the variance of s
2
x
(variance).
If you were then to divide that by s
2
x
, you would have 1, but this only holds true on
C
xy
depending on how close ∑(x – X) is to ∑(y – Y)
ii. N = number of scores in
x.
This should be the exact same number of scores in
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This note was uploaded on 04/17/2008 for the course PSC 204A taught by Professor Emelio during the Fall '07 term at UC Davis.
 Fall '07
 EMELIO

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