Graphs: probability of two vertices, chosen at random, of being connected by a link

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If I choose the vertices h and k in a simple graph uniformly, I know the probability of them being joined by an edge is $ \frac{2e}{n(n-1)} $ , where:

  • e is the number of edges in the graph,
  • n is the number of vertices,
  • n(n-1)/2 is the total number of possible links.

This is not true, in general, when the vertices are chosen randomly but not uniformly.

The question is, does the formula hold true if I choose h, k in a manner that is not directly influenced by their degree or neighbors, but still not uniformly?


Answered below: It really does depend on how I choose the vertices.

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It depends on what you mean by "directly influenced by". For instance, I could take the distribution that always picks a particular vertex p and then a particular vertex q. This doesn't seem to directly reference either their neighbors or degrees. The probability that the two vertices I pick "randomly" are connected by an edge is either 0 or 1 depending of whether or not p and q are actually adjacent.