CREATE TABLE table_18341 ("District" TEXT, "Incumbent" TEXT, "Party" TEXT, "First elected" FLOAT, "Result" TEXT, "Candidates" TEXT)

what year was the first elected incumbant Sidney R. Yates?
SELECT "First elected" FROM table_18341 WHERE "Incumbent" = 'Sidney R. Yates'
SELECT "First elected" FROM "table_18341" WHERE "Incumbent" = 'Sidney R. Yates'