Let us set stats education aside for a moment and make a cultural comment:
With great respect, xkcd has it wrong: a couple usually means either 1 or 3. From your youth:
- How long did you work on your homework? A couple of hours. (This means 1.)
- How many cookies did you take? Just a couple. (This means 3.)
Caveat: this is when referring to a small number of things (as opposed to a “couple” made of people).
A Best-Case Scenario 