Section 4

Statistics Functions

A word about the statistics functions: their use is based on an understanding of memory stack operation (Section 3). You will find that order of entry is important for most statistics calculations.

Probability Calculations

The input for permutation and combination calculations is restricted to nonnegative integers. Enter the y-value before the x-value. These functions, like the arithmetic operators, cause the stack to drop as the result is placed in the X-register.

Permutations. Pressing ´p calculates the number of possible different arrangements of y different items taken in quantities of x items at a time. No item occurs more than once in an arrangement, and different orders of the same x items in an arrangement are counted separately. The formula is

Py,x =

y!

( y x)!

 

Combinations. Pressing c calculates the number of possible sets of y different items taken in quantities of x items at a time. No item occurs more than once in a set, and different orders of the same x items in a set are not counted separately. The formula is

Cy, x =

y!

x!( y x)!

 

Examples: How many different arrangements are possible of five pictures which can be hung on the wall three at a time?

Keystrokes

Display

5 v3

3

´p

60.0000

Five (y) pictures put up three (x) at a time.

Sixty different arrangement possible.

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