Little Green Men and a Fella's Marriage Proposal - S6-E18
Character mistake: When Dr. Bell examines baby Constance, she has the stethoscope in her ears facing backwards. Also, when Sheldon and the professors are looking at the data from the telescope, Dr. Linkletter says "what about that" and Dr. Prakash says "no, that's within the standard deviation." That doesn't make sense.
Suggested correction: Not taking anything away from the other correction, but these are two separate mistakes put into one entry.
Additionally, a "standard deviation" is a significant concept that helps scientists determine when they have actual results worth investigating.