Chapter 9, Problem 27E

(a)

To determine

To find out the point by removing which, you could make the association appear to be stronger.

Answer to Problem 27E

That point is hippos.

Explanation of Solution

The scatterplot is given in the question which shows the relationship between the gestation period of non-humans in days and the life expectancy in years. The humans were removed from this as they were considered the outlier. Now, in the scatterplot the elephants and the hippos points are far from the other non-human species. So, we have to find that point by removing which we could make the association appear to be stronger. Thus, that point is hippos as by removing the point labeled hippos, the association becomes stronger as the hippos point has a greater residual compared to the elephants point.

(b)

To determine

To explain would the slope of the line increase or decrease.

Answer to Problem 27E

The slope would slightly increase.

Explanation of Solution

The scatterplot is given in the question which shows the relationship between the gestation period of non-humans in days and the life expectancy in years. The humans were removed from this as they were considered the outlier. Now, in the scatterplot the elephants and the hippos points are far from the other non-human species. The slope of the line would slightly increase as with the removal of the hippos point, correlation increases as the hippos point has a greater residual so therefore the slope will also slightly increase.

(c)

To determine

To explain should we keep just removing animals to increase the strength of the model.

Answer to Problem 27E

No, we should not remove the animals.

Explanation of Solution

The scatterplot is given in the question which shows the relationship between the gestation period of non-humans in days and the life expectancy in years. The humans were removed from this as they were considered the outlier. Now, in the scatterplot the elephants and the hippos points are far from the other non-human species.No, we should not keep just removing animals to increase the strength of the model because although the data isn't perfect, removing values without a justified reason isn't acceptable. By doing so, the model will give off a false impression and thus not represent a true model of gestation based on life expectancy.

(d)

To determine

To explain do you think elephants are an influential points.

Answer to Problem 27E

Yes, elephants are an influential point.

Explanation of Solution

The scatterplot is given in the question which shows the relationship between the gestation period of non-humans in days and the life expectancy in years. The humans were removed from this as they were considered the outlier. Now, in the scatterplot the elephants and the hippos points are far from the other non-human species. Yes, elephants are an influential points because due to the great change of slope of the regression line, the elephants point must have been influential as that is the definition of an influential point.