STAT 3006 Lecture Notes - Lecture 20: Regression Analysis, Statistical Hypothesis Testing
20 Nov 2018
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Document Summary
A leverage point is an observation with a value of x that is outlying among the x- values. An outlier is an observation of y that seems not to agree with the main trend of the data. Both can distort the fitted least squares line. A data point is influential if it unduly influences any part of regression analysis, such as the predicted responses, the estimated slope coefficients, or the hypothesis test results. Outliers and high leverage data points have the potential to be influential, but we generally have to investigate further to determine whether or not they are actually influential: example: see slr part 5 lecture notes. Points are influential if they drastically alter the slr line. Sometimes, one particular point may be an outlier, but it does not drastically the slr line if at all. The same goes with a point with high leverage.
