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Unformatted text preview: Hypothesis Testing with Correlation and Regression Plous (17,18) I believe r is how precise the line is. Examples are .2, .8 etc Five Steps to Hypothesis Testing • Step 1: Identify the research problem (hypothesis) o Describe the null and alternative hypotheses o For correlation null is that r=0 (no relationship) • Step 2: Decision Rule o Alpha level (.05 or .01) o Critical Statistic (e.g. critical r) value form table? • Step 3: Calculations • Step 4: Make decision whether r not to reject the null hypothesis o If observed r is bigger then critical r then reject null • Step 5: Conclusion o Tie findings back into research problem Finding a Statistically Significant Correlation • The result is “statistically significant” if: o The observed correlation is larger than the critical correlation We want our r to be big if we want it to be significantly different form zero. It can be either negative or positive but just as far away from zero o The p value is less than .05 (which is our alpha) o We reject the null hypothesis o Then we have support for our alternative hypothesis Correlation • Measure of how two variable cooccur and also can be used for prediction • Range is between 1 and +1 • The closer to zero the weaker the relationship and the worse the prediction • Positive of negative Positive Correlation • As values on one variable go up, so do values for other variable • Pairs of observations tend to occupy similar relative positions • Higher scores on one variable tend to cooccur with higher scores on the second variable • Lower scores on one variable tend to cooccur with lower scores on the second variable • Scatter plot shows clusters of point from lower left to upper right Negative Correlation • As values on one variable go up, values for the other variable go down • Pairs of observation tend to occupy dissimilar relative position • Higher scores on one variable tend to cooccur with lower scores on the second variable • Scatter plot shows clusters of point from upper left to lower right Zero Correlation • As values on one variable go up, values for the other variable go…anywhere • Pairs of observation tend to occupy seemingly random relative position • Scatter plot shows no apparent slope Correlation • The more closer the dots approximate a straight line, the stronger the relationship is • Perfect correlation= + or – 1.00 o One variable perfectly predicts the other o No variability in the scatter plot o The dots approximate a straight line Correlation Matrices • Correlation Matrix o Table showing correlations for all possible pairs of variables Finding a statistically significant correlation • The result is “statistically significant” if: o The observed correlation is larger than the critical correlation We want our r to be big if we want it to be significantly different from zero. This can be negative or positive. They are both equally far from 0 o The p value is less than 0.05 (which is our alpha) The p value is less than 0....
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This note was uploaded on 05/03/2011 for the course MGMT 276 taught by Professor Delaney during the Spring '08 term at University of Arizona Tucson.
 Spring '08
 Delaney

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