Without knowing the experiment details (number of trials, ratio of people laying vs telling the truth) we don't know if 50 is actually significant. What's the c

Without knowing the experiment details (number of trials, ratio of people laying vs telling the truth) we don't know if 50 is actually significant. What's the curve of success for participants assuming random guessing (in line with the proportion of liars)? Is 50 to be expected? My first thought is that with 20,000 participants, sheer chance will give you a handful of outliers, and 50 at 80% accuracy doesn't sound very high unless there were a very large number of trials per participant.