HP 39g+ - Manual (Page 156)

11-12 Using mathematical functions
Probability functions
COMB Number of combinations (without regard to order) of n
things taken r at a time: n!/(r!(n-r)).
COMB
(n, r)
Example
COMB(5,2) returns 10. That is, there are ten
different ways that five things can be combined two
at a time.!
Factorial of a positive integer. For non-integers, ! = Γ(x +
1). This calculates the gamma function.
value!
PERM Number of permutations (with regard to order) of n things
taken r at a time: n!/(r!(n-r)!
PERM (n, r)
Example
PERM(5,2) returns 20. That is, there are 20
different permutations of five things taken two at a
time.
RANDOM Random number (between zero and 1). Produced by a
pseudo-random number sequence. The algorithm used in
the RANDOM function uses a seed number to begin its
sequence. To ensure that two calculators must produce
different results for the RANDOM function, use the
RANDSEED function to seed different starting values
before using RANDOM to produce the numbers.
RANDOM
H I N T The setting of Time will be different for each calculator, so
using RANDSEED(Time) is guaranteed to produce a set of
numbers which are as close to random as possible. You
can set the seed using the command RANDSEED.
UTPC Upper-Tail Chi-Squared Probability given degrees of
freedom, evaluated at value. Returns the probability that
a
χ 2 random variable is greater than value.
UTPC (degrees, value)