Correcting Two-Variable Data.

Here is the raw data:

Week / Minutes of Advertising (x-values) / Sales (y-values)

1 / 2 / $1,400

2 / 1 / $920

3 / 3 / $1,100

4 / 5 / $2,265

5 / 5 / $2,890

6 / 4 / $2,200

This is the keystrokes used to enter the data into the HP 10bII Calculator:

**Correlation** can be calculated with the Yellow shift x,r key followed by SWAP key. In this example it is 0.89953 ( if set to 5 decimal places)

And covariance of x and y can be defined as:

cov xy = correlation* sigma(x) * sigma(y).

Here is the keystrokes to get sigma(x) and then sigma (y):

In this example, we have:

Sigma(x) = 1.63299

Sigma(y) = 773.12623

Covariance = 0.89953 x 1.63299 x 773.12623 = **1,135.66447**

Definition:

The **correlation** is one of the most common and most useful statistics. A correlation is a single number that describes the degree of relationship between two variables.

**Covariance** is a statistical measure of correlation of the fluctuations of two different quantities.