Standard Deviation Calculator for Population or Sample Data Sets

Standard Deviation Calculator Sign

This calculator will calculate the variance and standard deviation for either a population or a sample data set.

You can either enter the numbers in the data set one at a time, or you can copy and paste an existing data set (if separated by spaces, commas, line returns, or any combination thereof), or you can enter a number and its frequency (12x4, 8x6, 9x4).

Plus, unlike other online statistics calculators, this calculator will generate and display the step-by-step process used to calculate the results.

Read more ...

Standard Deviation Calculator

Calculate variance and standard deviation for population or sample data sets.

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Selected Data Record:

A Data Record is a set of calculator entries that are stored in your web browser's Local Storage. If a Data Record is currently selected in the "Data" tab, this line will list the name you gave to that data record. If no data record is selected, or you have no entries stored for this calculator, the line will display "None".

DataData recordData recordSelected data record: None
Enter or paste data set:Enter or paste data set:Enter or paste data set:Enter or paste data set:

Data set:

Enter each element of the data set (or paste a copied data set) into this text box. Be sure each number is separated by a space, a comma, a line return, or any combination of the three. Also, if you wish to enter a frequency for each number, enter the number, followed by a lowercase x, followed by the multiplier (for 3 number twos, enter 2x3).

Elements:# of elements:Number of elements in set:Numbers of elements in set:

Number of elements in set:

This is the total number of elements detected in the data set field.

Sum:Sum of numbers:Sum of numbers:Sum of numbers:

Sum of numbers:

This is the sum of elements detected by the Standard Deviation Calculator.

Average:Average (mean):Average (mean):Average (mean):

Average (mean):

This is the average or mean of the items within the data set. This is calculated by summing the items within the set, and then dividing the sum by the number of items.

Population var:Population variance:Population variance:Population variance:

Population variance:

This is the variance of the data set (also called the Mean of Squared Differences) if the items entered represent the entire (population) data set.

Pop std dev:Population std dev:Population standard deviation:Population standard deviation:

Population standard deviation:

This is the population standard deviation, which is calculated by finding the square root of the population variance.

Sample var:Sample variance:Sample variance:Sample variance:

Sample variance:

This is the variance of the data set (also called the Mean of Squared Differences) if the items entered represent only a portion (sample) of the data.

Samp std dev:Sample std dev:Sample standard deviation:Sample standard deviation:

Sample standard deviation:

This is the sample standard deviation, which is calculated by finding the square root of the sample variance.

If you would like to save the current entries to the secure online database, tap or click on the Data tab, select "New Data Record", give the data record a name, then tap or click the Save button. To save changes to previously saved entries, simply tap the Save button. Please select and "Clear" any data records you no longer need.

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Help and Tools

Learn

What variance and standard deviation are and how to calculate them.

Don't Let the Formula Scare You!

In my opinion, if the "powers that be" really wanted to entice kids into embracing mathematics, they would use kittens, puppies, bunny rabbits, etc., as math symbols, not Greek (geek) letters.

Want to scare a math-challenged student into closing the math textbook so fast that it blows out the candles in the room? Show them this:

σ2
N (Xi - μ)2
Σ
i=1
N
 
σ = √σ2

That's the scary-looking formula for calculating the variance (σ2) and standard deviation (σ) of a population data set.

But wait! Keep your candles burning!

As you will see in the example further down the page, the steps to calculating variance and standard deviation are much easier than trying to decipher the Greek/geek formula.

What is Standard Deviation?

Standard Deviation is simply one of several methods for summarizing the dispersion of the values in a set of data.

Specifically, standard deviation is the square root of the variance, which attempts to summarize the variability or dispersion of values relative to the mean of the entire set.

A small standard deviation indicates the values are tightly grouped around the mean (average) of the data set.

A large standard deviation indicates the values are not tightly grouped around the mean (average) of the data set.

Population Vs Sample Statistics

Population: The data set is the total set of elements of interest for a given problem. Population parameters in the formulas on this page are denoted by σ and μ.

Sample: The data set represents only a fraction of the population as defined above. Sample parameters in the formulas on this page are denoted by s and X.

4 Simple Steps

As I stated earlier, calculating standard deviation is much easier than the formula depicts. Here are the 4 simple steps:

  1. Find the mean of the data set.
  2. Find the sum of the squared differences from the mean.
  3. Divide the result in step #2 by n (population) or n - 1 (sample), where n is the number of items in the set.
  4. Find the square root of the result in step #3.

To see just how easy the above steps are, let me walk you through an example.

Example Problem

To illustrate how easy it is to calculate variance and standard deviation, I will use the following data set:

5, 4, 7, 9, 6, 8, 7, 5, 4, 5

Note: Decimals in this example are rounded to 2 places before they are displayed on the screen.

Step #1: Calculate the mean

The mean is the average of all numbers in a data set. To calculate the mean of a set of numbers, you add all of the items together and then divide that result by the number of items within the set.

Data set: 5, 4, 7, 9, 6, 8, 7, 5, 4, 5
Data set contains 10 items
Mean = (5 + 4 + 7 + 9 + 6 + 8 + 7 + 5 + 4) ÷ 10
Mean = 60 ÷ 10
Mean = 6
Step #2: Find the sum of the squared distances from the mean.

For each item in the data set we: (1) subtract the mean of the entire set from the item, (2) square the result, and then (3) sum all of the squared results, like this:


Cnt nXX - μ(X - μ)2
155 - 6 = -1(-1)2 = 1
244 - 6 = -2(-2)2 = 4
377 - 6 = 1(1)2 = 1
499 - 6 = 3(3)2 = 9
566 - 6 = 0(0)2 = 0
688 - 6 = 2(2)2 = 4
777 - 6 = 1(1)2 = 1
855 - 6 = -1(-1)2 = 1
944 - 6 = -2(-2)2 = 4
1055 - 6 = -1(-1)2 = 1
n = 10Sum = 60 Σ (X - μ)2 = 26

Step #3: Calculate the variance.

This step depends on whether or not the set you are working with represents the total data (population) or partial data (sample). Here is how you calculate the variance from the results in step #2 for either case (μ and X are both symbols for Mean, with the only real difference indicated by red text):

Population Variance (σ2)
 
σ2 =Σ (X - μ)2=26= 2.60
n10

Sample Variance (s2)
 
s2 =Σ (X - X)2=26= 2.89
n - 19

Step #4: Calculate the square root of the variance.

This step is basically the same for both the population and the sample standard deviation calculations. The only difference is that the Variance was computed differently in Step #3 (n in denominator vs n - 1):

Population Standard Deviation (σ)
 
σ = √σ2= √2.60= 1.61

Sample Standard Deviation (s)
 
s = √s2= √2.89= 1.70

See how easy that was?

Adjust Calculator Width:

Move the slider to left and right to adjust the calculator width. Note that the Help and Tools panel will be hidden when the calculator is too wide to fit both on the screen. Moving the slider to the left will bring the instructions and tools panel back into view.

Also note that some calculators will reformat to accommodate the screen size as you make the calculator wider or narrower. If the calculator is narrow, columns of entry rows will be converted to a vertical entry form, whereas a wider calculator will display columns of entry rows, and the entry fields will be smaller in size ... since they will not need to be "thumb friendly".

Show/Hide Popup Keypads:

Select Show or Hide to show or hide the popup keypad icons located next to numeric entry fields. These are generally only needed for mobile devices that don't have decimal points in their numeric keypads. So if you are on a desktop, you may find the calculator to be more user-friendly and less cluttered without them.

Stick/Unstick Tools:

Select Stick or Unstick to stick or unstick the help and tools panel. Selecting "Stick" will keep the panel in view while scrolling the calculator vertically. If you find that annoying, select "Unstick" to keep the panel in a stationary position.

If the tools panel becomes "Unstuck" on its own, try clicking "Unstick" and then "Stick" to re-stick the panel.