What is the correct question to ask?

Concerning redheads in the room, I would ask this question:

Given these past historical trends, and a new room with people (operating under the same trends), what is the most likely percentage of redheads that it will contain?

That is the only meaningful application I can make of this example.
Already you see that neither solution is the correct one, because the quantity of redheads isn't governed by the historical concentration of redheads, but by another factor - in this case, a constant.

Have you heard of this saying, "If you torture the data enough, it will confess to anything?" So take a step back, look at your data, and think about the relationships therein. Formulate your question correctly.