Final answer:
Outliers are data points that diverge significantly from other data points in a set, and influential points are a subset of outliers that significantly influence the regression line. The correct multiple-choice answer about outliers is 'd) A and B only'.
Step-by-step explanation:
Outliers are data points significantly different from the other data points in a set. They may be the result of errors or abnormalities or hold crucial information about the dataset. Influential points are outliers that significantly impact the regression analysis by affecting the slope of the regression line or the correlation coefficient. According to a rule of thumb, a potential outlier is a point further than two standard deviations of the residuals from its predicted value on the least squares regression line.
For the multiple-choice question, the correct answer is 'd) A and B only' because outliers:
- Do not conform to the pattern of the other points,
- Affect the position of the line or curve of best fit,
It is not always correct to discard outliers, as they may provide valuable insights or highlight the need for further investigation.