TI82 Users Guide
Random Numbers from the Home Screen
The rand command: Press the $button\; and\; the\; left\; arrow\; to\; select\; the\; probability\; menu.\; The\; top\; entry\; is\; the\; random\; operator\; command.\; If\; you\; presswhile\; the\; "1:\; rand"\; is\; highlighted,\; the\; 82\; will\; write\; "rand"\; on\; the\; home\; screen.\; If\; you\; pressagain,\; you\; will\; see\; a\; number\; between\; zero\; and\; one.$
Press
While random numbers are frequently used in mathematical simulations, we often want numbers other than from zero to one. We will briefly show you how to create numbers in any range you wish.
CHANGING THE INTERVAL: If we wish to have real numbers in some other interval, all we have to do is multiply the rand by an appropriate value, and perhaps add or subtract something. Here are the commands that can be entered to produce numbers from each of the following intervals. Try each command on the calculator and press enter several times to see the output.
For numbers in the interval 
Use the expression 
0< number <10 
10*rand 
1 
1+9*rand 
6< number<20 
6+14*rand 


Notice that we add enough to get the first value, and then we multiply by a number equal to the interval width (top  bottom). These produce real decimal values. If we wish to produce only integers we need to add one more menu selection to our palette.
The int command: Press $,,\; and\; 4\; and\; the\; calculator\; prints\; the\; command\; "int".\; This\; is\; the\; greatest\; integer\; function\; you\; may\; have\; studied\; in\; school.\; For\; positive\; integers,\; it\; simply\; removes\; the\; decimal\; fraction\; leaving\; the\; largest\; integer\; less\; than\; the\; value.\; Try\; each\; of\; the\; following\; and\; test\; the\; results:$
Int( 3.5) int (4.234) int( 3.2) surprised? For negative values, the greatest integer function drops down to the next integer lower than the value, but for 3.2, the next lower integer IS 4. Get used to this if you wish to work with negative integers.
Now try the commands below and see what happens as you repeatedly press
For Integers in the interval (including endpoints) 
Use the expression 
010 
int(11*rand) 
110 
int (10*rand)+1 
620 
int (15*rand)+6 
:
Notice that we have had to add one more to the interval to make the values on both ends print. If we only used int(14*rand)+6 we would get numbers from 6 up to 19.
SOME PRACTICE PROBLEMS: Now you need to see if you can make the calculator pick some random numbers. Be careful, we have thrown in a few tricky ones… but don't worry, the answers are down the page, and if you get really stuck, ask your teacher or send Mr. Ballew an email letter with a really clear question.
There are some additional methods you will learn as we go along to pick values and strings of values, but if you have mastered all of these, your well on the way to being able to simulate probabilities on the calculator.
CAREFUL… WE STORED THE ANSWERS DOWN HERE… DON'T LOOK BEFORE YOU REALLLLLLY TRY TO ANSWER THE QUESTIONS
In the next unit I'll show you how to use the list menu's to print and store long strings of random numbers and some other sequences.