Texas Instruments TI-89 User Manual

Activities

775

Simulation of Sampling without Replacement

This activity simulates drawing different colored balls from an urn without replacing them.
Detailed information about the steps used in this example can be found in the electronic
chapter Programming.

Sampling-without- Replacement Function

In the

Program Editor

, define

drawball( )

as a function that can be called with two

parameters. The first parameter is a list where each element is the number of balls of a
certain color. The second parameter is the number of balls to select. This function
returns a list where each element is the number of balls of each color that were selected.

:drawball(urnlist,drawnum)
:Func
:Local templist,drawlist,colordim,

numballs,i,pick,urncum,j

:If drawnum>sum(urnlist)
:Return “too few balls”
:dim(urnlist)

colordim

:urnlist

templist

:newlist(colordim)!drawlist
:For i,1,drawnum,1
:sum(templist)

numballs

:rand(numballs)

pick

(continued in next column)

:For j,1,colordim,1
:cumSum(templist)

urncum

:If pick



urncum[j] Then

:drawlist[j]+1

drawlist[j]

:templist[j]

templist[j]

:Exit
:EndIf
:EndFor
:EndFor
:Return drawlist
:EndFunc