An engineer, a psychologist and a research scientist were hiking in the hills of Scotland. On the hillside, they saw a black sheep. "All the sheep in Scotland are black!" declared the engineer. "No! One sheep in Scotland is black," said the psychologist. "You are both wrong," said the research scientist. "At least one sheep in Scotland is black, on one side anyway."

Moral: Don't make assumptions in research.

What other assumptions do we make?