Can anyone help me with Chapter 9, question 28C? In Excercise 26 we saw that Vic

Question

Can anyone help me with Chapter 9, question 28C? In Excercise 26 we saw that Vicki Keith's round-trip swim of Lake Ontario was an obvious outlier among the other one-way times. Here is the new regression after this unusual point is removed: Dependent variable is: Time R-squared = 4.1%         s = 292.6 Variable              Coefficient Intercept             -11048.7 Year                     6.17091 a) In this new model, the value of se is much smaller. Explain what that means in this context. b) Now would you be willing to say that the Lake Ontario swimmers are getting faster (or slower)? Can anyone help me with Chapter 9, question 28C? In Excercise 26 we saw that Vicki Keith's round-trip swim of Lake Ontario was an obvious outlier among the other one-way times. Here is the new regression after this unusual point is removed: Dependent variable is: Time R-squared = 4.1%         s = 292.6 Variable              Coefficient Intercept             -11048.7 Year                     6.17091 a) In this new model, the value of se is much smaller. Explain what that means in this context. b) Now would you be willing to say that the Lake Ontario swimmers are getting faster (or slower)?

Explanation / Answer

a) Unusual points in a regression often tell us more about the data and the model otherthan any other points. Before removing the unusual point, the standard error is S = 443.770 After removing the unusual point (Vicky keith's round trip considered as a outlier), the standard error is S = 292.610. Errors in the predictions based on this model have a standard deviation of 292.6 minutes. This means that after removing the outlier the standard deviation value is decreases more. But deleting the unusal point can gives a false sense of how well the model is fits the data. our goal should be understanding the data, not making standard error is small enough as you can. b) No, because all the values in the data represents there is no significant variation among the independent and dependent variables.

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