Correlation & Regression

A fifth grade science teacher wants to know if there is a relationship between final exam scores and overall coursepoints after adjusting for a quiz score.

In order to determine whether there was a significant relationship between overall coursepoints and final exam scores, after controlling for quiz scores, a hierarchical regression was run. All assumptions were assessed using SPSS. There was independences of residuals, as assessed by a Durbin-Watson statistic of 1.08. An examination of various scatterplots indicated a general linear relationship between variables of interest, although perfect linearity was not observed.

Overall Scatterplot

Partial Regression Plot: Final Exam Score & Quiz Score

Figure 3. Partial Regression Plot: Final Exam Score & Course Points

The assumption of homoscedasticity was violated, as the scatterplot in Figure 1 demonstrates (i.e., the values were not evenly spread across the scatterplot). There was no evidence of multicollinearity as evidenced by no...
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