The position of the graphically represented keys can be found by moving your mouse on top of the graphic.
Turn your calculator on  
Press . (It says ON on top of the key.)  
Clearing the memory  
Press , you should see CSR above the key. (CSR stands for Clear Statistical Registry) 
Entering data  
one variable  
Enter a data element and press (if you need to delete an element, type it in, then press . The screen will tell you how many numbers you've entered. Do the same with the rest of the list.  
two variables  
The TI25X does not do regression. 
Calculating onevariable statistics  
mean (x)  
Press . You should see x over the key.  
standard deviation for populations (s or s_{n})  
Press . You should see s_{n }over the key.  
standard deviation for samples (s or s_{n1})  
Press . You should see s_{n1} over the key. 
Calculating twovariable statistics 

r (correlation)  
The TI25X cannot do correlation.  
regression coefficients  
slope  
The TI25X cannot do regression.  
yintercept  
The TI25X cannot do regression. 
Calculating combinations and permutations  
combinations (nCr)  
The TI25X cannot do combinations.  
permutations (nPr)  
The TI25X cannot do permutations. 
Turning the calculator off  
This is a solar calculator. It does not turn off. (If you cover it, it will turn off by itself in about two minutes.) 
Worked Out Examples
In the following examples, we list the exact key sequence used to find the answer. We will list the keys by the main symbol on the key. In parentheses, we will list a helpful mnemonic, e.g. we will list e^{x} as (e^{x}).
A: What is the mean and standard deviation of the following list of numbers?
15 16 20 21
1: Clear Memory  (CSR) 
2: Enter Data 

3: Compute the mean  ( x ) 
4: Compute the standard deviation (population)  (s_{n}) 
5: Compute the standard deviation (sample)  (s_{n1}) 
You should get a mean of 18, population standard deviation of
2.549509757 and a sample standard deviation
of 2.943920289.
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