That is the problem. It can be the same exact product just a different randomly selected subset of people (or even same people who slept better last night) and

That is the problem. It can be the same exact product just a different randomly selected subset of people (or even same people who slept better last night) and you could get wildly different feedback. Reading the book, I thought there was too much faith being put on instantaneous observations, which is are very noisy signals just due to the fact that the world is random.