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Unformatted text preview: 3/20/2008 1 Regression Psyc110 March 20, 2008 Outline Correlations cont’d. ◦ Review ◦ Hypothesis testing Regression introduction ◦ Prediction ◦ Regression equation Regression coefficients ◦ Accuracy of prediction Correlation Review Scatterplot used to display associations visually Covariance formula: similar to variance, but includes sum of cross-products instead of sum of squares Correlation coefficient = r = standardized covariance ◦ Ranges from -1.00 to +1.00 ◦ Sign = direction of relationship ◦ Value = strength of relationship Positive Negative ? ?? = ¡? − ? ¢£ ( ? − ? ¢ ) − 1 ¤ = ? ?? ¥ ? ¥ ? 3/20/2008 2 1) Use formulas to calculate cov XY and r XY 2) Compare calculated r to value in Table D.2 ◦ df = N-2 ◦ Always two-tailed (unless you hear differently) Reject if calculated r is more extreme than tabled r Can be positive or negative (must add minus sign for negative r ) Hypothesis Testing with Correlations As always, using Greek letters to denote hypothesized population values Population correlation coefficient = ρ (rho) For variables X and Y, written as...
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This note was uploaded on 05/05/2008 for the course PSYCH 110 taught by Professor Burt during the Spring '08 term at Vermont.
- Spring '08