Put the create table in the statement:
PREPARE STMT FROM "CREATE TABLE tab_derived_1 SELECT * FROM tab_1 WHERE predict_var = '4' or predict_var = '2' union
(SELECT * FROM tab_1 WHERE predict_var = '0' or predict_var = '1' ORDER BY RAND() limit ? )" ;
EXECUTE STMT USING @sample;
And if you want to return the results, not just store them in a table, just do a final
SELECT * FROM tab_derived_1