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Cheat Sheet 2 Pam 210

# Cheat Sheet 2 Pam 210 - Alvin Poyser PAM 210 Prelim 2...

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Alvin Poyser PAM 210 Prelim 2 Chapter 2: Association- two variables are assoc. if some values of one variable tend to occur more often with some values of the other variable. Response variable - measures an outcome of a study. Explanatory variable- explains or causes changes in the response variables. Scatter plots: Outlier: An individual observation that falls far away from the pattern. Positive relationship : Above average values of one variable tend occur with above average values of the other variable and below average values of one variable also tend to occur with below average values of the other variable. Negative relationship : Above average values of one variable tend to occur with below average values of the other variable and vice versa. Correlation coefficient ( r ) gives us a numerical measurement of the strength of a linear relationship between the explanatory and response variables Correlation does not distinguish between response and explanatory variables. Both variables must be quantitative . r does not depend on units of measurement Values of r are always between -1 and 1 r is greatly affected by extreme values or outliers Least sqr regressions: we have a bunch of observations on an explanatory variable, x , and a response variable, y. We need to find the line: y= a+bx (a, is intercept, b is slope) 2 types of prediction are In sample : For a value of the explanatory variable that is within the observed range of that variable, but not actually observed. & Out of sample : For a value of the explanatory variable that is outside of the range of values actually observed. This is usually referred to as

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