Cannot complete Exercise 3 in Using ArcMap tutorial

Description

When working with Exercise 3 of the Using ArcMap tutorial, step 4 of the section titled 'Adding a field to an attribute table' returns the error below.

"Failed to add the field to the table/feature class. Cannot create a table with a duplicate column. Field 'POP_DEN' already exists in the table 'tracts'".

Cause

There is already a column named POP_DEN in the tracts attribute table.

Solution or Workaround

1. Right-click tracts in the table of contents.
2. Select Open Attribute Table.
3. Right-click the heading for the POP_DEN field in the tracts attribute table.
   
   

   Note:
   If you have already completed the 'Joining tables' section of the tutorial and joined the tracts and tract_pop tables, right-click the heading for the tracts.POP_DEN column.

   
   
4. Select Delete Field.
5. Click the Yes button on the Confirm Delete Field dialog box. It is now possible to add the new POP_DEN field to the tracts attribute table.