I hope it’s not too early in the thread to tell my second favorite joke, which I believe I first read years ago here on the dope.

A group of epidemiologists and a group of biostatisticians are both going from Boston to Philly for a public health conference. Both groups decide to take the train. When they get to the train station in Boston, each of the epidemiologists has a ticket, but they notice that the biostatisticians have but one ticket among them. “How do you ever think you’ll all get to Philly with just one ticket?” the epidemiologists ask. “We have our methods,” reply the statisticians.

They get on the train and after a while they hear the conductor coming down the aisle asking for tickets. Suddenly, all the statisticians jump up out of their seats and run into the tiny lavatory at the back of the car. When the conductor enters the car, he notices the “occupied” sign on the lavatory, knocks on the door, and says, “Ticket, please!” The door cracks open, the statisticians slide out the ticket, the conductor punches it and slides it back. After he goes into the next car, the statisticians come out of the lavatory and go back to their seats, grinning smuggly at the epidemiologists.

After the conference, both groups meet back at the train station in Philadelphia. Of course, the epidemiologists have only bought one ticket this time, but they see that the biostatisticians have NO ticket whatsoever. “How do you ever think you’ll get back to Boston without any ticket?” ask the epidemiologists. “We have our methods,” reply the statisticians.

Once on board the train they again hear the conductor coming, and all of the epidemiologist jump up out of their seats and crowd into the tiny lavatory in the back of the car. The biostatisticians jump up and crowd into the other tiny lavatory across the aisle, all except one, who knocks on the door of the lavatory containing the epidemiologists, and says “Ticket, please!” The epidemiologists crack open the door and slide out the ticket, which the statistician grabs, then she runs into the other lavatory with all the other statisticians and closes the door just as the conductor enters the car.

Obviously, the biostatisticians return to Boston safely, while the epidemiologists are all thrown off the train in Newark. The moral of the story is: Never attempt to apply statistical methods until you understand the underlying principles.