“The Big Bang Theory” and “Young Sheldon” were the top-rated and most-watched scripted shows on broadcast Thursday night, according to Nielsen data. Airing at 8 p.m., “Big Bang Theory” averaged a 2.6 rating in adults 18-49 and 13.2 million viewers. “Young Sheldon” followed at 8:30 with a 2.1 and 11.7 million viewers.