HP 50g manual Chapter Probability Distributions, MTH/PROBABILITY.. sub-menu part, r +

Chapter 15

Probability Distributions

In this Chapter we provide examples of applications of the pre-defined probability distributions in the calculator.

The MTH/PROBABILITY.. sub-menu - part 1

The MTH/PROBABILITY.. sub-menu is accessible through the keystroke sequence „´. With system flag 117 set to CHOOSE boxes, the following functions are available in the PROBABILITY.. menu:

In this section we discuss functions COMB, PERM, ! (factorial), and RAND.

Factorials, combinations, and permutations

The factorial of an integer n is defined as: n! = n⋅ (n-1) ⋅ (n-2)…3⋅2⋅1. By definition, 0! = 1.

Factorials are used in the calculation of the number of permutations and combinations of objects. For example, the number of permutations of r objects from a set of n distinct objects is

n Pr = n(n − 1)(n − 1)...(n − r + 1) = n! /(n − r)!

Also, the number of combinations of n objects taken r at a time is

⎛ n ⎞		=	n	n −		n −		n − r +	1) =	n
⎜	⎟		(		1)(		2)...(			!
⎜	⎟						r!			r!(n − r)!
⎝ r ⎠

We can calculate combinations, permutations, and factorials with functions COMB, PERM, and ! from the MTH/PROBABILITY.. sub-menu. The operation of those functions is described next:

•COMB(n,r): Calculates the number of combinations of n items taken r at a time

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