[dba-SQLServer] SQL Server indexes

Am I correct that in a given column, 'Y' and NULL is the "same as" 'Y' and
'N' or 'Y' and '' (empty string) as far as usefulness of an index goes?  IOW
all three of these examples are "two choices" and thus would likely not
benefit from an Index for selection speed?
 
John W. Colby
Colby Consulting
www.ColbyConsulting.com