How to set multiple entity references as default values using the hook_form_alter() I have a node which when renders an adds an entityform to the page.

The node has a entity ref field which references multiple other nodes. (eg: Products A, Product B, Product C, etc)

What I need is a rating from each user for each product who views the node.

Eg : 
Node 1 | User 1
Product A : rating1
Product B : rating2
Product C : rating3

Node 1 | User 2
Product A : rating4
Product B : rating5
Product C : rating6

How could i establish such a thing?
You can use Fivestar and Voting API for rating the product 

The Fivestar voting module adds a clean, attractive voting widget to nodes and comments and any entity