Correlations Notes 11-28-06

Correlations Notes 11-28-06 - I Notes for Stats II Intro to...

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I. Notes for Stats (11-28-06) 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 y, because they are both taken from the same participant.
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