CREATE TABLE table_11647327_2 (head_of_household VARCHAR, single VARCHAR)

What is the range of the head of household whereas single is $171,551 $372,950?
SELECT head_of_household FROM table_11647327_2 WHERE single = "$171,551–$372,950"
SELECT "head_of_household" FROM "table_11647327_2" WHERE "$171,551–$372,950" = "single"