Some first year university students come home from holiday for a surprise math test of 'What's 2 + 2?'

The engineer says, "Well it's 3.75, but given the situation we can round it to 5."

The mathematician goes and works for a while, then comes back saying, "I don't know what the answer is, but I know one exists."

The astrophysicist says, "Rounding to the nearest million, the answer would be 0."

The psychology student says, "Can we talk about why you are asking this question?"

The finance student subtly asks, "What do you want the answer to be?"

The sociology student wants to know the implications of this question.

The medical student, who is the last to answer, says, "Well that's easy, it's 4. I memorized it."