[CSMastermind]

> This assumes that people read books completely at random.

I'm not sure it implies that. I think that if:

1. Book quality follows a normal distribution.

and

2. People are capable of accurately assessing the quality of books relative to other books.

then you'd end up with an average rating of 2.5.

It doesn't matter if people are disproportionately reading the better books and rating them highly because an increasing number of reviews on a book would only give you more confidence in its rating, not change the rating of the book relative to other books.

To illustrate this we can imagine a world with only 100 books in it and only 100 people in it.

Let's assume that a single person from that group reads all 100 books and per the two assumptions above correctly rates them on a normal distribution.

Then the other 99 people read only a single book which the first person recommends as a 5. And per the two assumptions above they all also rate it as a 5.

Now there are 99 books with only 1 rating normally distributed between 1 and 5 and there is 1 book with 100 ratings - all 5s.

Does this change the average rating of books on the platform?

Nope the average rating is still 2.5. In fact the one book could have a million ratings or a billion 5 star ratings and the average rating of books on the platform would still be a 2.5.

What we see on sites like goodreads is that either book quality doesn't follow a normal distribution and/or people are not capable of accurately assessing the quality of books relative to other books.

[Retric]

You missed #3 all books get rated.

Terrible books likely have fewer readers, thus fewer and likely zero people would post a review.

[therealdrag0]

Good points. But do we have evidence GR is not a normal distribution. GP’s comment does apply to views of ratings, so we might have an impression if higher average rating because the books we look at are more often better than avg.