What makes examples good for novices? and How do we tell if an example is good for novices?

So I am taking a P2PU course On How to Teach Web Programmin to Free Range
Learners<http://p2pu.org/en/groups/how-to-teach-webcraft-and-programming-to-free-range-students/>and
a couple of questions came up:

So I pose them to the community:

   1. What makes examples good for novices?
   2. How do we tell if an example is good for novices?

Also where can I find a good set of examples for learning programming?

It would be nice to have a curated set of "Great literature".

Pointers to any research on the topic would be appreciated.

Stephen