Quik efficiency calculation question

let's say we have a for loop from 1 to n, in which there's an if condition that in the first case leads to 3 actions and in the other case to just one.

The magnitude of this would be O(n), but what about the equation?
Do we just pick the worse case and make it O=3n? If not then how do we calculate it?

 

Theoretically, yes, I think you take the worst case scenario. However applied in the real world, the efficiency would be somewhere between n and 3n.