Indeed, and one way to improve that is to separate the random variable that represents the population by different random variables (say male immigrant with at least master level studies, female of less than 30 years, other males, other females) and calculate the success rate of each.
They may have a different probability distribution, even if the population average follow a normal law (central limit theorem)
If you invest is the most achieving group instead of distributing your investment across the population, you will have better returns.
They may have a different probability distribution, even if the population average follow a normal law (central limit theorem)
If you invest is the most achieving group instead of distributing your investment across the population, you will have better returns.