After removing the outlier and looking at the log-transformed sales, the correlation is now positive but still not significantly different from 0.

However, the customer demographics for trucks and automobiles are different, and the reasons for buying a truck or a car may not be the same. It's worthwhile to look at another scatterplot, this time marking trucks and autos separately.

To produce a scatterplot of Log-transformed sales by Fuel efficiency, controlling for Vehicle type, recall the Simple Scatterplot dialog box.

Deselect Sales in thousands and select Log-transformed sales as the y variable.

Select Vehicle type as the variable to set markers by.

Click OK.

The scatterplot shows that trucks and automobiles form distinctly different groups. By splitting the data file according to Vehicle type, you might get a more accurate view of the association.