In this article, we explain how to calculate the S_{xx} value in Excel. The S_{xx} value refers to the sum of squares of deviations due to X. It can be calculated using the formula,

**S _{xx }= ∑(X_{i} – X̅)^{2}**

In order to calculate S_{xx} in excel we first calculate the **mean** of the dataset using the **=AVERAGE(Range)** function where *Range* is the range of the data values.

We then take the difference of the data values from the mean and square them. The sum of the resulting values is equal to S_{xx}.

**Step 1: Enter the Data Values and find the Mean**

Suppose that the given data values are: *1, 1, 2, 6, 8, 9, 13, and 18*. We enter the data values into column A as shown below.

Calculate the mean of the data value in cell D2 using the command

**=AVERAGE(A2:A9)**.

The mean of the data values terms out to be 7.25.

**Step 2: Calculate the Square of the Deviations**

We calculate the **(X _{i} – X̅)^{2}** values in the column B.

Enter the following formula in column B2,

**=(A2-$D$2)^2**

This will calculate the value **(X _{1} – 7.25)^{2}** = 39.0625.

Drag the cursor down up to ROW 9 to calculate all the square deviation values.

**Step 3: Find S**_{xx} by Summing the Values

_{xx}by Summing the Values

We have found all the **(X _{i} – X̅)^{2}** values in the column B, from cell B2 to cell B9. Now we add up all these values to calculate the value of S

_{xx}.

Go to cell D5 and type the following command,

**=SUM(B2:B9)**.

We obtain the Sxx value in cell D5. We conclude that,

**S _{xx }= 259.5**