dmar

Well I think I misunderstood the question. Here it says "in 5 year period the annual return on an investment" which implies that return is not only for 5 years, it could be for more years. However, if it is mentioned like "annual returns on 5 years investment" and 5 observations are given, then that is a population.

Previous comment was very general with respect to sample and population that if only data sets are given then that's a population unless otherwise stated.