What is the difference between the two, are they intеrchangable?
I heard this dialogue in a movie:
- Someone spilled coke on the transmitter
- It was beer. I would think.
Could he just say "I think"?
So, if he says in your example, "I think," the implication is that he's making the observation based on the evidence in front of him: the color, the smell...
If he says - as he did - "I would think" - it implies that he's making the assumption based on information arrived at prior to the event, like knowing the workers that were on duty are notorious drinkers, or that he knows there was a party that preceded their arrival.