# How to Download the invT Function on a TI Calculator

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The invT function on a TI calculator is a function that allows for the computation of the critical "T" value of a T distribution when dealing with hypothesis testing and confidence intervals. While the TI-84 calculator comes standard with the InvT function, the previous generations of this graphing calculator--the TI-83 and TI-83 Plus--do not. The best way to get the function into your calculator is to program it in manually.

Skill level:
Easy

### Things you need

• TI-83 or TI-83 Plus Calculator

## Instructions

1. 1

Press the [PROGRAM] button to enter program mode on your calculator. Select the "New" option and press [ENTER]. Type in the name "INVT" at the name prompt and hit [ENTER]. The calculator should now be in edit mode.

2. 2

Press [PROGRAM] and select the "I/O" option. Scroll the cursor to the "Input" option and press [ENTER]. Type the following string into the first line after the "Input" command exactly as written: "AREA LEFT: " ,A . The previous period is simply there to end the last sentence and should not be included. The quotations marks must be included. Remember that for alpha input you'll want to hit the [ALPHA] before selecting the character. When finished, press [ENTER]. A new line will begin.

3. 3

Press [PROGRAM] and select the "I/O" option. Scroll the cursor to the "Input" option and press [ENTER]. Type the following string into the first line after the "Input" command exactly as written: "DF: " ,D . Press [ENTER].

4. 4

On the new line, press [1], then press [STORE], and type in "S." The line will display as: 1->S . Press [ENTER].

5. 5

Press [PROGRAM] and scroll to the "If" option. Press [ENTER]. Type in "A" . Press [SECOND] and then press [CATALOG]. Arrow up until you find the less than ("<") symbol. Highlight it and press [ENTER]. Type in ".5" and press [ENTER].

6. 6

Press [PROGRAM] and scroll down to the "Then" option. Hit [ENTER] once to select the option. Hit [ENTER] a second time to begin a new line.

7. 7

Type in "-1" then press [STORE], and then "S." The line should appear as "-1->S". Press [ENTER].

8. 8

Press [PROGRAM] and select the "End" option. Press [ENTER] once to select and again to begin a new line.

9. 9

Press [SECOND] and then [CATALOG]. Select the "abs" function and press [ENTER]. Type in the following line exactly as written: 2A-1) . Next, press [STORE] and type "A." The entire line should appear as: abs(2A-1)->A . If the line appears correctly, press [ENTER].

10. 10

Press [STAT], scroll to the "TESTS" sub-menu and select the Tinterval function. Press [ENTER]. This function takes four arguments separated by commas. Press "0" and then type in ",". Next, press [SECOND] and then [x^2] to get the square root function. After the opening bracket for this function, type "D+1)" to put in the argument and end the function. Type in "," to separate from the next argument. Finally, type the following line exactly as written: (D+1),A . This takes care of the final two arguments. The entire line should appear as: Tinterval 0,sqrt(D+1),(D+1),A . If this is correct, press [ENTER].

11. 11

Press [PROGRAM] and scroll to the "I/O" option. Select the "Disp" function and press [ENTER]. Press [VARS] and select the "Statistics" sub-menu (by pressing [ENTER] once highlighted). Select the "TEST" option and then scroll to "upper" variable. Press [ENTER] to select. Press the multiplication key [] and type in "S" . The entire line should appear as: Disp upperS . Once this is correct press [ENTER].

12. 12

Press [SECOND] and then [QUIT]. The invT function is now in your TI-83 calculator and ready to run.

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