I think the author correctly understood probability theory.
If a population is modelled by a random variable, each individual probability is unknown. What is known is the continuous probability distribution of the entire population.
Intuitively, this means you cannot know which individuals will succeed or fail, you can only know what proportion will succeed -- regardless of the merits of each individual.
The author correctly calculated mean outcome -- more precisely, expected value:
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.
If a population is modelled by a random variable, each individual probability is unknown. What is known is the continuous probability distribution of the entire population.
Intuitively, this means you cannot know which individuals will succeed or fail, you can only know what proportion will succeed -- regardless of the merits of each individual.
The author correctly calculated mean outcome -- more precisely, expected value:
http://en.wikipedia.org/wiki/Expected_value#Univariate_conti...