Thoughts on the World

How My Rankings Work

I score each book out of 10 using six factors:


How well does the book tackle the subject? Does it keep focused? Is there any unnecessary bias or opinionated writing?


How easy is the text to read? Did I have to work hard against poor grammar or usage? Did I have to keep on referring to a glossary or looking up terms?


Is the book nicely laid out? Are the illustrations and tables clear? Has care been taken with proof-reading and editing?


Is the book thought-provoking? Does it give me ideas which I might be able to use, possibly in a different context?

Value for money

Does the book represent value for money? (A poor but cheap book might do OK here!)

Did it do what it said on the box?

This is the "bottom line". Did I feel that this book delivered on my expectations? Am I better for reading it?

I was intrigued by the idea of using "Chernoff Faces", a mechanism invented by the statistician Hermann Chernoff to represent complex data for comparison. It relies on the human brain's ability to recognise faces and their expressions, which is sensitive to quite small variations. 

Faces are drawn by a program which has ten parameters (each in the range 0-1):

All Zeros

All Ones

All 0.5

However, if you just use the raw scores as parameters, you get a variety of strange expressions, most of which look sad or angry. I wanted my faces to represent how I  feel about  the books. I've therefore come up with the following relationship between my six factors, and the Chernoff face parameters:

head eccentricity x 10  =  5 (fixed)
eye eccentricity x 10  = 5 + (5 - Presentation / 2)
pupil size x 10  = 5 + (5 - Readability / 2)
eyebrow slant x 10  = 5 + (5 - Content / 2)
nose size x 10  = 5 (fixed)
mouth shape x 10  = Did it do what it said on the box?
eye spacing x 10  = 5 (fixed)
eye size x 10  = 10 - Ideas
mouth length x 10  = Value for money
mouth opening x 10  = 10 (fixed)

For more about Chernoff faces see my links page.