HP 49g Manual: Understanding Probability Distributions with Factorials and Combinations

Models: 49g

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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)…321. 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

 

 =

(

− 1)(

 

− 2)...( −

+ 1) =

!

n

n n

 

n

 

n

r

n

 

 

 

 

 

 

 

 

 

 

 

 

 

r!

 

 

 

r!(n − r)!

 r

 

 

 

 

 

 

Page 15-1

Page 153
Image 153
HP 49g Chapter Probability Distributions, MTH/PROBABILITY.. sub-menu part, Factorials, combinations, and permutations