Check Excel to see if the Data Analysis ToolPak has been activated.  Go to the Data tab at the top of the screen and click on it to see if there you can select ‘Data Analysis’.  If so, you are all set.  If not, activate it using the following directions for a PC:

1) Menu File > Options.
2) In the dialog Excel Options, click on the list item ‘Add-ins’.
3) In the list Add-ins, click on the button Go….
4) In the dialog Add-ins, check the box ‘Analysis ToolPak’.
5) Click the button OK.

For a Mac:

1.  Go to Tools menu > Add-ins.
2. Put a check beside “Analysis ToolPak” and then click OK.