Answer Happy

15) To evaluate their model, the researchers plotted some model diagnostics. a) Do you see any violations of the standard regression assumptions in the residual plot below? Explain. 00650 Residuals vs Fitted 80 2008 ം ആ ആ ആ യാമം മൂ ०००० Residuals o o O -1000 7300 024 T T T 230 190 200 210 220 240 250 260 Fitted values Im(force - feedback + perseverance + wais) b) Here are the added variable plots, also called partial plots. Evaluate whether your interpretation of the model slopes reported in Q2 should change. Added-Variable Plots 1065 656 101 8 O we - O o 0 000 O O force others O 80 og oto 090 O 27 8 O O 029 229 T -0.4 -0.2 0.0 02 04 4 -2 0 2 2 feedback others perseverance others 055 o Ooo % O 0 50 220 force others 8676 Oo O O 0 o O 00 O 929 4 -2 0 2 2 4 6 wais others

c) Here is a histogram of the leverage values for the model. Is the distribution centered where it should be? What is the average leverage for this model? Leverage Values Frequency 0 15 0.02 0.04 0.06 0.08 0.10 0.12 hatvalues(mod1) d) The highest leverage point in the is about 0.12. Looking at the added value plots in part (b), do you think it is more likely that case 29 or case 9 has the higher leverage value? Explain your reasoning e) Here are the dfbetas for feedback. Explain what these values represent. Is it a problem that they are centered around 02|| DFBetas for Feedback Frequency 0 15 30 -0.4 -0.2 0.0 0.2 0.4 dfbetas(mod1), 2]