The Analysis ToolPak is an Excel add-in that provides data analysis tools for statistical and financial functions. It is usually installed by default, but if it is not, you can install it by following these steps:
In the Manage drop-down list, select Excel Add-ins, and then click Go...
(If the Analysis ToolPak is not listed in the Add-Ins available box, click [Browse...], locate it in the list of available add-ins, and then select it.)
(Make sure that you select both check boxes in the dialog box.)
(Click OK to close both dialog boxes.)