What is the type of scam where a con artist sells different advice to two groups of people?

The root of such a scam is to provide investment recommendations for the purpose of eventually selling an expensive newsletter or service.

For example, suppose the perp sends a recommendation to 8,000 people. Half are told to buy and half are told to sell. After it plays out, the process is repeated with the 4,000 people who got the correct advice. And then once again with 2,000.

When done, 1,000 people have received 3 out of 3 correct picks and they are pitched an expensive tout recommendation service for say $995. If only 20 sign up, that's nearly $20g. 50 is $50k.

Before the popularity of the internet, the odds of any of the 8,000 people meeting each other was infinitesimal, especially if 160 people in each US state received the tout. I'd guess that the odds are higher in the internet era but still fairly low.

And even if people came across one another, the odds of getting caught are modest because these are pop up events. Perps don't use their actual home or business addresses. A PO Box is likely and the entire scam is transient. Do it, hopefully receive some checks and like many scams, they move on to the next PO Box.

It is called an A/B Test lol.

This is not a scam just a rip off.

Unless they forgot to write the disclaimer "not investment advice, consult your financial advisor", then its a scam.