CREATE TABLE table_41674 ("Poll Source" CLOB, "Date ( s )  administered" CLOB, "Sample size" FLOAT, "Margin of Error" CLOB, "Mel Martinez  ( R ) " CLOB, "Betty Castor  ( D ) " CLOB)

What is the highest sample size administered on October 18?
SELECT MAX("Sample size") FROM table_41674 WHERE "Date(s) administered" = 'october 18'
SELECT MAX("Sample size") FROM "table_41674" WHERE "Date(s) administered" = 'october 18'