8 - Prediction Part 2 - Quick Recap We want to predict a...

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Unformatted text preview: Quick Recap We want to predict a score on Y ( Y ) based on a score on X. We can use the equation for a straight line to make this prediction (assuming linear relationship) Y = bX + a Want to find the line that minimizes the distance between itself and all Y scores Finding the Regression Line What values must we use for our line in order to find the regression line? One option: Use the standard scores of Y and X z Y = r z X In this formula, r = slope of the line Remember that z scores are centered around the mean (z of 0 = raw score mean) Therefore, intercept of this formula = 0 For r = 0, z Y will always be zero Can generalize If r (or b) equals zero, Y will always be mean of Y z y = rz x is conceptually useful, but difficult to predict with. We will use a raw score formula to find our regression line z Y = r z X is Q Q Q Q Q Q Q Q- =- X Y S X X r S Y Y ' Solving for Y gives us the following: Raw Score Regression Formula Y X S S r X S S r Y X Y X Y +- = 220d Y X S S r X S S r Y X Y X Y +- = 220d b a...
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This note was uploaded on 04/17/2008 for the course PSY 201 taught by Professor Arthur during the Spring '08 term at Purdue University-West Lafayette.

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8 - Prediction Part 2 - Quick Recap We want to predict a...

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