The position of the graphically represented keys can be found by moving your mouse on top of the graphic.  Row 1 starts with the SHIFT key.

Turn your calculator on
	Press .
Clearing the memory
	Press while in SD mode.

Entering data
	one variable
		Press sets the calculator in SD mode. You should see a 0 on the screen. Enter your list, pressing after each number. (The word DATA appears above the key.) The number on the screen should increase by one for each number you enter.
	two variables
		The Citizen SR-135 does not do two-variable statistics.

Calculating one-variable statistics
	mean (x)
		Press . You should see x above the key in red.
	standard deviation for populations (s or sn)
		Press . You should see sn above the key (on the right) in red.
	standard deviation for samples (s or sn-1)
		Press . You should see sn-1 above the key (on the left) in red.

Calculating combinations and permutations
	combinations (nCr)
		No direct commands, but we can use the factorial function. Enter the n-value and press . (You should see x! above the key.) Press and enter the r-value. Press . Enter the value of n-r and press .
	permutations (nPr)
		No direct commands, but we can use the factorial function. Enter the n-value and press . (You should see x! above the key.) Press . Enter the value of n-r and press .

Turning the calculator off
	Press .

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
2: Enter Data
3: Compute the mean	(x)
4: Compute the population standard deviation	(sn)
5: Compute the sample standard deviation	(sn-1)

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

1:Compute 10C6	(4 = 10-6)
2: Compute 9P5	(4 = 9 - 5)

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

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