So, how many outbound links is the optimal number? Does it matter that they link to a lower or higher authority page comparing to yours?
I haven't read the exact no. of outbound link should be on a page. What I consider about links on a page is There should not be more that 100 link ( Suggested by Google, check webmaster tool) There should be a balance between i/b & o/b links. Links should be to similar/relevant sites. If links are important then mark them nofollow. Let see what others say ...
Its good to link to Wikipedia to give reference and you can make those links Nofollow like <a href="http://wiki......com/" rel="nofollow">wiki-word</a> Code (markup):