> There was a stock broker looking for new business. He cold called 512 people (he must have been a quant); half he told to sell X stock, half he told to buy. The next week he called the 256 for whom he'd made the right prediction and did the same again: Half he told to sell, half to buy ... several weeks later he was down to 16 people. He called all of them and said, 'look, I was right 5 times in a row ...'.

Except, what you just described is a scam and not something a registered broker can do.