Week 3 2.1-2.5
Popular in Elementary Probability and Statistics I
Popular in Mathematics (M)
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This 1 page Class Notes was uploaded by Alan Nguyen on Saturday September 19, 2015. The Class Notes belongs to MAT 221 - M300 at a university taught by in Summer 2015. Since its upload, it has received 48 views.
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Date Created: 09/19/15
is a scatterplot ofthe regression residuals against A is the difference between an observed value of the the response variable and the value predicted by the regression line explanatory variable Residual plots help us assess the fit of a residual observed y predicted y regression line An is an observation that lies outside the overall pattern of the other observations 0 Outliers in the y direction have large residuals Outliers and Influential Points An observation is influential if the removal of such points would markedly change the result of the calculation Caution about Correlations and Regression I Both describe linear relationships I Both are affected by outliers I Always plot the data before interpreting I Beware of extrapolation I Use caution in predicting y when x is outside the range of observed x s I Beware of lurking variables I These have an important effect on the relationship among the variables in a study but are not included in the study I Correlation does not imply causation Part 2 Page 1 I Ideally there should be a quotrandomquot scatter around zero I Residual patterns suggest deviations from a linear relationship A lurking variable is a variable that is not among the explanatory or response variables in a study and yet may influence the interpretation of relationships among those variables Example In an analysis of damage caused by house fires it was found that the more firefighters that are sent to a fire the greater the damage Are the firefighters causing extra damage