The position of the graphically represented keys can be found by moving your mouse on top of the graphic. 

Turn your calculator on
Press The A C Key:Row 4, Column 5. (You can see ON written in white to the right of the AC key.)
Clearing the memory
Press The Shift Key: Row 1, Column 1 It's all black. Row 4 Column 5 (You should see SAC above the key.)

 

Entering data
one variable
Press Row 1 Column 2 Row 7 Column 2 (you'll see SD is the upper right corner of the screen). Enter the first number in your list and press Row 7 Column 5. Enter the second number in your list and press Row 7 Column 5. Continue until you're done with your list.
two variables
The 250HC does not do two-variable statistics.

 

Calculating one-variable statistics
mean (x)
Press Row 1 Column 1 It's all black. SHIFT is written above the key. Row 4 Column 1 (you should see x above the key).
standard deviation for populations (s or sn)
Press Row 1 Column 1 It's all black. SHIFT is written above the key. Row 4 Column 2 (sn appears above the key).
standard deviation for samples (s or sn-1)
Press Row 1 Column 1 It's all black. SHIFT is written above the key. Row 4 Column 3 (sn-1 appears above the key). 

Calculating two-variable statistics
r (correlation)
The 250HC does not do two-variable statistics.
regression coefficients
slope
The 250HC does not do two-variable statistics.
y-intercept
The 250HC does not do two-variable statistics.


Calculating combinations and permutations
combinations (nCr)
Enter the n value. Press Row 1 Column 1 It's all black. SHIFT is written above the key. Row 6 Column 2 (you should see nCr above the key). Enter the r value and press Row 7 Column 4. 
permutations (nPr)
Enter the n value. Press Row 1 Column 1 It's all black. SHIFT is written above the key. Row 6 Column 1 (you should see nCr above the key). Enter the r value and press Row 7 Column 4.

 

Turning the calculator off
Press Row 1 Column 6.

 

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 ex as (ex).


A: What is the mean and standard deviation of the following list of numbers?

15      16      20      21

1: Clear Memory  Row 1 Column 1 It's all black. SHIFT is written above the key. Row 4 Column 5 (SAC)
2: Enter the data  Row 1 Column 2 Row 7 Column 2 Row 6 Column 1 Row 5 Column 2 Row 7 Column 5 Row 6 Column 1 Row 5 Column 3 Row 7 Column 5 Row 6 Column 2 Row 7 Column 1 Row 7 Column 5 Row 6 Column 2 Row 6 Column 1 Row 7 Column 5
3: Compute the mean  Row 1 Column 1 It's all black. SHIFT is written above the key. Row 4 Column 1 (x)
4: Compute the population standard deviation.  Row 1 Column 1 It's all black. SHIFT is written above the key. Row 4 Column 2 (sn)
5: Compute the sample standard deviation:  Row 1 Column 1 It's all black. SHIFT is written above the key. Row 4 Column 3 (sn-1)


    You should get a mean of 18, population standard deviation of 2.549509757 and a sample standard deviation of 2.943920289.

 

C: Find 10C6 and 9P5.
1: Compute 10C6  Row 6 Column 1 Row 7 Column 1 Row 1 Column 1 It's all black. SHIFT is written above the key. Row 6 Column 2 (nCr) Row 5 Column 3 Row 7 Column 4 
2: Compute 9P5  Row 4 Column 3 Row 1 Column 1 It's all black. SHIFT is written above the key. Row 6 Column 1 (nPr) Row 5 Column 2 Row 7 Column 4


You should get 10C6 = 210 and 9P5= 15120.

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