The Profs and the Zebra

A bunch of distinguished professors were visiting the Hwange National Park. They drove out on the savannah in their jeep, stopped and scouted the horizon with their binoculars.
Suddenly the engineering prof shouted ``Look! There's a herd of zebras! And there, in the middle : A white zebra! It's fantastic! There are white zebras ! We'll be famous!''
The biology prof replied ``I wonder if its offspring have stripes?''
The physics prof punched his calculator and said ``It should take four and a half cans of paint to get the stripes back on.''
The chemistry prof quickly worked out a new paint formula that would make just four cans of paint sufficient.
The statistics prof added ``It's not significant. We only know there's one white zebra.''
The maths prof made his contribution ``Actually, we only know there exists a zebra, which is white on one side.''
But the Park Ranger with them said ``Oh, so that's where my horse went!''