Find the difference between the number of female senators and representatives born between 1930 to 1970.
difference = SUBTRACT(SUM(type = 'sen' WHERE gender_bio = 'F' AND strftime('%Y', birthday_bio) between '1930' and '1970'), SUM(type = 'rep' WHERE gender_bio = 'F' AND strftime('%Y', birthday_bio) between '1930' and '1970')); female refers to gender_bio = 'F'; senators refers to type = 'sen'; representatives refers to type = 'rep'; born between 1930 to 1970 strftime('%Y', birthday_bio) between '1930' and '1970';
SELECT SUM(CASE WHEN T2.type = 'sen' THEN 1 ELSE 0 END) - SUM(CASE WHEN T2.type = 'rep' THEN 1 ELSE 0 END) FROM historical AS T1 INNER JOIN `historical-terms` AS T2 ON T1.bioguide_id = T2.bioguide WHERE T1.gender_bio = 'F' AND strftime('%Y', T1.birthday_bio) BETWEEN '1930' AND '1970'