**Some Useless Gifts**

Master Stem was reviewing the work of his students. He stopped and examined the calculations of Student Leaf. "What is this number here?"

"It is a p-value, Master Stem."

"Explain to me how you calculate this number."

"The p-value represents the probability of getting a sample result or a result more extreme. In this sample, I got a value of 2, so I added the probabilities for 2 and all the smaller values."

"So this value here represents the probability of a zero?"

"Yes, Master Stem."

"And the next is the probability of a one?"

"Yes, Master Stem."

"And this is the probability of a two?"

"Yes, again, Master Stem."

"I understand the last probability, Student Leaf, but these others are strange."

"As I said before, Master Stem, they represent probabilities of events more extreme than the result in the sample."

"Do you recall, Student Leaf, the gifts that I received last year from my graduating students?"

"Yes, most of them were strange. One student gave you a dog collar, but you do not own a dog. Another student gave you a pipe, but you do not smoke."

"I do enjoy these gifts, even though they are useless. I also enjoy your calculations, even though they are equally useless"

"Why are these calculations useless, Master Stem."

"Your sample had a value of two and yet you calculate probabilities for other events that did not happen."

This work is licensed under a Creative Commons Attribution 3.0 United States License. It was written by Steve Simon and was last modified on 2017-06-15. Category: Teaching resources