Predicting the weather has always been a difficult task. However, there are some weather facts that intuitively make sense. One, for example, is that the farther South one travels towards the equator, the warmer it will get. But, what if we were interested in how much temperature changes as one travels South. Or, how does the temperature change as on travels from East to West?

The picture to the right is an explanation of terms you will need to know for this lesson. The latitude is measured in degrees North of the equator. The equator would be 0 and the North Pole is 90. Longitude is measured in degrees West of the prime meridian. In this case, the prime meridian is measured as 0 and numbers increase East to West up to 180. For example, Chicago, IL is 42 degrees latitude (or North of the equator) and is 88 degrees longitude or ( West of the prime meridian.)

To help answer the questions above, we can use a statistical term called **covariance**. In this lesson, you will learn the ideas behind covariance and how to calculate it. Before we start this temperature problem, let's use GSP to investigate the concept of covariance.

Click here to return to the VARIANCE lesson.