Problem

1. An analyst fits an RF classifier where some of the features include seasonally adjusted employment data. He aligns with January data the seasonally adjusted value of January, etc. What "sin" has he committed?

2. An analyst develops an ML algorithm where he generates a signal using closing prices, and executed at close. What's the sin?

3. There is a 98.51% correlation between total revenue generated by arcades and computer science doctorates awarded in the United States. As the number of doctorates is expected to grow, should we invest in arcades companies? If not, what's the sin?