Probability is one thing, likelihood another - but I compute them in pretty much the same way.
If the historicity of Jesus is dubious, I might give it a likelihood of 0.2
I might give the story that Jesus travelled to India a likelihood of 0.1, just on its own merits (and I think I'm being generous there).
That gives them a combined likelihood of 0.2 x 0.1 or 0.02
The likelihood that no-one said anything about this extended absence is independently about 0.05, I think.
Given the very poor correlation between his teachings and Indian thought, the likelihood that Indian teachings influenced Christianity is, independently again, about 0.05.
The combined likelihood of all these statements is 0.2 x 0.1 x 0.05 x 0.05, or 1 in 20 000
I didn't do the sums until just now, as a demonstration. My real thought processes were more like, 'that's unlikely and that's
very unlikely so, taken together, they are so improbable that I can dismiss them.'
Okay, folks, can we get back to the dharma?