HP 10bII+ Financial manual Probability Calculations, Factorial, Permutations

If BEST FIT is selected, the 10bII+ calculates the best fit when \Z, \W, or

\Tis pressed. When selected, BEST FIT flashes briefly, followed by the chosen fit. The

selected regression will remain set until a new one is selected, or the statistics memory is cleared.

When the statistics memory is cleared using \t, the current regression model is set back to LINEAR.

Probability Calculations

In many probability calculations, specific methods of counting possible outcomes are required as part of a process to determine the likelihood of certain results. The three main operations that allow this are:

• ! factorial

•nPr permutations

•nCr combinations

Factorial

Factorial (!) is a mathematical operator that instructs you to multiply the current number by all previous whole numbers. Writing out so many numbers can be cumbersome, so mathematicians use ! to signify this process. For example:

5! is equivalent to 5 x 4 x 3 x 2 x 1 = 120.

On the 10bII+, the input value n must be within -253 < n < 253. The gamma function is used to calculate n! for non-integer or negative values.

Permutations

The nPr function calculates the number of different arrangements, or permutations, of n items taken r at a time. No item can occur more than once in a set of r items, and different orders of the same r items are counted separately. This is calculated using the formula:

PERMUTATIONS =	n!
	(-----------------n– r)!

126 Statistical Calculations