An Introduction to Econometric Theory

AThe Binomial Coefficients

Given a positive whole number , the product of all the whole numbers from 1 up to is called factorial, denoted by the symbol . In other words,

Also, by convention , so is defined for . The sequence goes 1, 1, 2, 6, 24, 120, 720, 5040, 40320, …, and thereafter gets large very rapidly.

One may think of as the number of different ways of picking objects one at a time from a basket containing objects without replacing them. There are ways to pick the first one, ways to pick ...