Regression_Sp08_BB

Regression_Sp08_BB - Linear Regression"I always avoid...

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Linear Regression Regression “I always avoid prophesying beforehand because it is a much better policy to prophesy after the event has already taken place.” - Winston Churchill Prediction • Regression is about improving our prediction of scores • Regression uses scores on a measure that is correlated with your variable of interest to improve your prediction Prediction Variables Var predicted Var predicted from to Name Predictor variable Criterion variable Symbol XY Example SAT scores College grades Prediction • If you want to predict a person’s score on a given measurement, what is your best estimate of what that score will be? – The mean • What is your best estimate of variability (accuracy) of this prediction? – The standard deviation Example • How many times did Mike exercise last week? • From last class… mean was 7 • BUT, Mike rated himself as a 6 on the “fit, active” self-concept (1 to 7) • We would adjust our estimation to above the mean This is Mike
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Regression Line Ŷ = a + (b) (X) Ŷ = predicted score on Y • a = regression constant – Y intercept • b = raw-score regression coefficient – slope Regression Line Ŷ = a + (b) (X) Ŷ = predicted score on Y • a = (mean of y) – b (mean of x) • b = COVxy/ s 2 x Regression Line Regression Example Participants viewed a video of a comedian telling a joke. They were told that the researchers were selecting jokes for future research. In actuality, the subjects were being videotaped and their facial expressions were being recorded. Independent raters blind to the joke
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This note was uploaded on 04/07/2008 for the course PSY 031 taught by Professor Dicorcia during the Spring '08 term at Tufts.

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Regression_Sp08_BB - Linear Regression"I always avoid...

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