ArtsAutosBooksBusinessEducationEntertainmentFamilyFashionFoodGamesGenderHealthHolidaysHomeHubPagesPersonal FinancePetsPoliticsReligionSportsTechnologyTravel

What is Standard Deviation

Updated on January 31, 2013

Deviation means 'how far from the normal' or to put it another way 'how spread' out are the range of numbers in the sample you are looking at or analysing. This term 'spread out' is also called 'volatility.'

Imagine the numbers were the heights of trees or the heights of people in a school class, so they are all different heights when measured, when you add them all up and divide by how many there are you find out the normal height or 'the Average' or 'the Mean.'

Standard Deviation is then used to tell you how spread out the numbers are.

What is standard deviation used for

Standard deviation is often used on a sample to estimate the value for everybody or for the whole population of what is being measured or estimated. For example using trees if you wanted to know how many trees are in a big big forest you could count them all but this would take forever.

Standard Deviation is widely used, in analysis of people and diseases, in voting, in investment and money, in the stock market, anywhere it is necessary;-

  • to estimate the overall numbers

  • to estimate the level of risk

  • to estimate the level of volatility

Practical Example 1

Using the forest and trees again, if it was time to harvest a section of the forest for trees of particular height research would be conducted and Standard Deviation used as a way to reduce the risk. In this case the statistics would show that there approximately so many trees of the height required in the section planning to be harvested.

A project manager may well ask for research in a number of sections to pick the best, that is the one where the Standard Deviation has the least volatility.

So What

People working with trees need information like this to allow them to classify the trees, to reduce the risk of cutting the wrong place. You will often see a table of data that started off with someone calculating the Standard Deviation.

You could measure all the trees one by one but that would be tedious and boring..

What a scientist or statistician will do is select a sample and then use Standard Deviation to estimate the numbers for the entire forest. This is an important and accepted scientific method of figuring out the characteristics of a large group or population of things when it is almost impossible to count them all.

Tree Population in Section XYZ

Tree Type
Height Range
No. Per Acre
Est. Diameter
23 inches
17 inches
9 inches

For example if samples were taken and all the trees were divided into Large, Medium and Small their characteristics could then be estimated

  • their height range,

  • the number per hectare or acre

  • their estimated diameter.

These estimates are calculated using Standard deviation and from these will come projected or anticipated timber yields when they are about to be harvested.


    0 of 8192 characters used
    Post Comment
    • Drax profile imageAUTHOR

      des donnelly 

      7 years ago from NYC....

      DW... I've made my living with Excel and analysing stats for years, it is as much pleasure as anything to work with a decent set of complex numbers. They are like an old foreign comrade, after a time you understand the unspoken, the nuances...



    • profile image


      7 years ago from Colorado


      Don't be threatened by statistics like standard deviation. Its just simple math. But what it represents is a powerful tool that will help you make better decisions and develop better understandings.

      Good luck.


    • Drax profile imageAUTHOR

      des donnelly 

      7 years ago from NYC....

      thanks for the comment Doc.. I was looking at your Ch4 there and it is very comprehensive, I must go back and read it in detail and the others. I am away to the attic now to look for my slide rule... ;-) just joking... !!

    • profile image


      7 years ago from Colorado


      I wrote Statistics Made Easy - Really here on hubpages about 2 months ago. Chapter 4 is the one dealing with the Measures of Dispersion in which Standard Deviation resides.

      Simply put, a standard deviation is the difference between a score (or observation) from the mean of all of the scores (or observations). It reflects the variability of all of the scores about the mean. It is the square root of the variance.



    This website uses cookies

    As a user in the EEA, your approval is needed on a few things. To provide a better website experience, uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

    For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at:

    Show Details
    HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
    LoginThis is necessary to sign in to the HubPages Service.
    Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
    AkismetThis is used to detect comment spam. (Privacy Policy)
    HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
    HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
    Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
    CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
    Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the or domains, for performance and efficiency reasons. (Privacy Policy)
    Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
    Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
    Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
    Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
    Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
    VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
    PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
    Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
    MavenThis supports the Maven widget and search functionality. (Privacy Policy)
    Google AdSenseThis is an ad network. (Privacy Policy)
    Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
    Index ExchangeThis is an ad network. (Privacy Policy)
    SovrnThis is an ad network. (Privacy Policy)
    Facebook AdsThis is an ad network. (Privacy Policy)
    Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
    AppNexusThis is an ad network. (Privacy Policy)
    OpenxThis is an ad network. (Privacy Policy)
    Rubicon ProjectThis is an ad network. (Privacy Policy)
    TripleLiftThis is an ad network. (Privacy Policy)
    Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
    Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
    Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
    Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
    ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
    Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)
    ClickscoThis is a data management platform studying reader behavior (Privacy Policy)