Table schema:
CREATE TABLE table_name_5 (sample_size INTEGER, date VARCHAR, republican VARCHAR, margin_of_error VARCHAR)

Question: What is the sample size of the poll taken on Dec 13-15, 2007 that had a margin of error of more than 4 and resulted with Republican Mike Huckabee?
SQL: SELECT AVG(sample_size) FROM table_name_5 WHERE republican = "mike huckabee" AND margin_of_error > 4 AND date = "dec 13-15, 2007"