# Probability Simulation Settings Editor on the TI-84 Plus

The Probability Simulation on the TI-84 Plus application contains four simulators (Tossing Coins, Rolling Dice, Picking Marbles form an urn, and Spinning a Spinner) that work much the same way. Some information is common to these four simulators.

## Trial Set option on the Settings editor

Most Settings editors in the Probability Simulation application contain the **Trial Set **option. With this option, you tell the application how many trials you want it run whenever you tell it to toss coins, roll dice, pick marbles, or spin a spinner.

For example, if you are tossing two coins and **Trial Set** is 5, the first time you tell the application to toss the coins, it tosses the two coins five times, thus executing five trials. The next time you tell it to toss the coins, it tosses the coins five more times for a total of ten trials, and so on.

Similarly, if you are rolling dice and **Trial Set** is 5, then each time you tell the application to roll dice, it will roll the dice five times.

If **Trial Set **is 1, then, after you tell the application to perform the first trial, you are given the option of tossing the coins one time, ten times, or 50 times. If **Trial Set** is greater than 1, then each time you tell the application to execute a trial, it executes the number of trials specified by the **Trial Set **setting.

## Graph and table settings on the Settings editor

Most of the Settings editors in the Probability Simulation application contain options that you can use to tell the application how you want it to display the graph and the table of the data it collects. These options are

**Graph:**With this option, the application graphs your data as a histogram and gives you the choice between having the*y*-axis of the histogram display the*frequency*of an outcome or the*probability*of an outcome.For example, if you toss one coin eleven times and it lands heads up six times, then in a frequency histogram the bar depicting the “heads” outcome is six units tall; in a probability histogram, it is 6/11 units tall. When setting the options in the Settings editor, select

**Freq**if you want the graph displayed as a frequency histogram; select**Prob**for a probability histogram.**StoTbl:**This option tells the application how many rows you want to see when your data is displayed in a table. You are given a choice between seeing no rows, all the rows, or only 50 rows. If you select 50 rows, only the bottom 50 rows of the table (your most recent data) can be viewed as you scroll through the data in a table.But let’s face it, the TI-84 is a powerful puppy; it can handle displaying

*all*the rows in the table. So there is no harm in setting the**StoTbl**option to**All**. It won’t slow things down one bit.**ClearTbl:**This option is obvious; it affords you the opportunity to tell the application if you want to clear the table or not. Your only choices are**Yes**and**No**. However, if you make changes to other options in the Settings editor,**ClrTbl**is automatically set to**Yes**.**Update:**This option enables you to tell the application to update the graph and table after 1, 20, or 50 trials, or at the end of the probability experiment. Because the TI-84 is a fast calculator, set this to 1.

## Weighted outcomes in the Advanced Settings editor

The Advanced Settings editor is where you tell the application if you want it to toss fair or weighted coins, roll fair or weighted dice, or spin a spinner divided into equal or unequal sections. The first picture depicts the weights for a fair marble and the second picture shows the weights for a spinner divided into four equal sections.

To bias a coin, die, or spinner, change the weight of the outcome. For example, to bias a die so that it is twice a likely to display 6 as it is to display any other number, set the weights of sides 1 through 5 to 1 and the weight of side 6 to 2.

To change the weights of the outcomes listed in the Advanced Settings editor, use the arrow keys to place the cursor on the existing weight in the second column of the Advanced Settings editor, use the keypad to enter the new weight, and then press **[ENTER]**.

The number you enter for the weight must be a positive integer. As you enter the weights, the application updates the probability of the outcome in the third column.