Review/revise test yourself sections

[amyheather]

Feedback from Fatemeh (#134):

I very liked the easy to understand language of the book and the "Test yourself" section! The latter made the book interactive. Just as a suggestion, having the answers/solutions for the tests, would be helpful for improving learning experience. There is an educational application for ISO called "Mimo", which uses the coding tests for learning purposes, it might be worth to take a look for some more test yourself examples. I know that the book is not meant to be a coding tutorial, but some people (including me) might be not professional coders, and these test might be helpful for them.

I think readers usually follow along with the codes provided, so they won't be challenged for the Test yourself sections like the one provided in the following image:

RE: input modelling page: Just a suggestion: It might be helpful to have a different dataset in "Test yourself", to be practiced with solutions provided. It would have been helpful to map and test understanding in another different example

I need to review and revise these sections... some pages missing them... some pages have Q&A... some have separate tasks... some just say go back and do the page...