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Unit 7: Linear RegressionLesson 1:Prediction vs. Theory Testing : 

Unit 7: Linear RegressionLesson 1:Prediction vs. Theory Testing EDER 5210 – Educational Statistics Dr. Robin K. Henson University of North Texas © 2002 University of North Texas Dr. Robin K. Henson © 2002 Used with permission. www.jasonlove.com Next Slide

Correlation coefficients relationship : 

Correlation coefficients relationship Pearson r Foundation of regression (and all other classical stats.) Regression Correlational method that uses r to predict variables University of North Texas Dr. Robin K. Henson © 2002 Next Slide

Two Uses of Regression : 

Two Uses of Regression Prediction – identify variables that account for (predict) the DV. Can information on a predictor variable predict what someone scores on a DV? University of North Texas Dr. Robin K. Henson © 2002 Next Slide

How can we take GPA and see if it can predict success? : 

How can we take GPA and see if it can predict success? University of North Texas Dr. Robin K. Henson © 2002 Next Slide 1 + 2X

Linear Equation : 

Linear Equation a weight “additive” Y intercept b weight “multiplicative” slope University of North Texas Dr. Robin K. Henson © 2002 Next Slide

How far off is the prediction? : 

How far off is the prediction? Error Score How well does Perfectly, r=1.00 9 7 5 3 0 0 0 0 University of North Texas Dr. Robin K. Henson © 2002 Next Slide

Predict adult height from height at age 2? : 

Predict adult height from height at age 2? But not perfect pred. * Measure height at age 2 and 21. * Use weights on next group of 2 years olds. University of North Texas Dr. Robin K. Henson © 2002 Next Slide

Theory Testing - test expected relat. between predictors and a DV. : 

Theory Testing - test expected relat. between predictors and a DV. Self-efficacy Prior Ach. Strong Positive Weak Math Ach. University of North Texas Dr. Robin K. Henson © 2002 Next Slide

Prediction : 

Prediction Theory Testing What are the purposes of the research? University of North Texas Dr. Robin K. Henson © 2002 Next Slide

Slide 10: 

University of North Texas Dr. Robin K. Henson © 2002 Go to next slide for answer. Click mouse to continue Q: Suppose a researcher conducts a study to see if reading achievement of 3rd graders on a standardized test is predictable by decoding skill and a measure of vocabulary recognition. Because the research believes that phonics-based instruction is more useful for achievement on this particular test, he/she expect a stronger relationship between decoding skill and achievement than vocabulary recognition and achievement. After conducting the study, the researcher found r = .45 between decoding and achievement and r = .23 between vocabulary recognition and achievement. Is this primarily a prediction or theory-testing use of regression/correlation? Was the researcher’s hypothesis supported? How do you know?

Answer : 

Answer A: This is best considered a theory-testing use of regression/correlation because the researcher is examining a specific theory/hypothesis about the variables. Do not be confused by the word “predictable,” all regression uses see if variables can predict dependent variables, but the purposes of the research can vary. The researcher is probably happy with his/her results because decoding had a stronger correlation than vocabulary recognition. Just how much stronger could be evaluated by squaring both coefficients and seeing how different they are in terms of variance explained between the variables. If you do this, then decoding can explain 20% of achievement variance and vocabulary recognition can explain 5% of achievement variance. Depending on the context of the study, of course, this is probably a big enough difference to take note of. Click mouse to go to next slide.

Unit 7: Linear RegressionLesson 1:Prediction vs. Theory Testing : 

Unit 7: Linear RegressionLesson 1:Prediction vs. Theory Testing EDER 5210 – Educational Statistics Dr. Robin K. Henson University of North Texas © 2002 University of North Texas Dr. Robin K. Henson © 2002 Used with permission. www.jasonlove.com End

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