Temperature and latitude
The least squares line is shown on this scatterplot and the locations of the cities are shown on a linked map — clicking a cross also selects the city on the map and vice versa.
Identify the locations of the four 'outliers' whose temperatures are much higher than predicted by the LS line. Note that Jacksonville's latitude was wrongly recorded in the original data set (38 degrees instead of 30 degrees). Click Correct Jacksonville to set its latitude to the correct value. Mention that the LS line changes little.
State that the first thing you should do when an outlier is detected is to check the data.
You could also mention that many of the other high residuals (crosses above the LS line) are in the Northwest — perhaps they should be removed and analysed separately?
This data set contains the maximum January temperature (degrees Fahrenheit) and latitude (degrees north of the equator) for various cities in the USA, as published in the book Data Analysis and Regression, by F.Mosteller and J.W.Tukey in 1977.