Quiz: Why the statistics professor sued the baker...

[Harald]

There once was a statistics professor. Every morning he bought his breakfast rolls at the local bakery. But then he retired, got bored and started weighing the rolls before he had breakfast.
He discovered that sometimes the rolls were below the weight the baker advertised. So one day he told the baker he would have to sue him if he didn't stop selling underweigth rolls.
The baker said it would never happen again, the professor continued weighing the rolls and in deed never again found a roll that was to light. He still sued the baker though - why?

No, the first one to give the correct answer does not get a roll