A large sample size of people isn't necessary to verify the ability.

Case in point, the woman who can smell Parkinson's disease, to some ridunculous p-value.

http://www.scientificamerican.com/article/one-woman-s-abilit...

It's not anecdotal if it's consistently repeatable. You would only need hundreds of people if you were trying to prove that everyone could do it.

You can measure the probability of achieving the result at random and determine the statistical significance of your experiment. Being able to successfully anticipate a call within 10 seconds in a 2 hours interval yields a p < 0.01

Some effects published in medical journals have a less convincing p-value.

And ensure that he records all the false positives