What is the highest sample size administered on October 18?
CREATE TABLE table_41674 (
    "Poll Source" text,
    "Date(s) administered" text,
    "Sample size" real,
    "Margin of Error" text,
    "Mel Martinez (R)" text,
    "Betty Castor (D)" text
)
SELECT MAX("Sample size") FROM table_41674 WHERE "Date(s) administered" = 'october 18'
Below are sql tables schemas paired with instruction that describes a task. Using valid SQLite, write a response that appropriately completes the request for the provided tables. ### Instruction: What is the highest sample size administered on October 18? ### Input: CREATE TABLE table_41674 (
    "Poll Source" text,
    "Date(s) administered" text,
    "Sample size" real,
    "Margin of Error" text,
    "Mel Martinez (R)" text,
    "Betty Castor (D)" text
) ### Response: SELECT MAX("Sample size") FROM table_41674 WHERE "Date(s) administered" = 'october 18'