What is Standard Deviation Formula?

The formula of standard deviation is below

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Where:

  • xi = Value of each data pointx̄ = MeanN = Number of data points

  • Standard deviation is most widely used and practiced in portfolio management services. For example, fund managers often use this basic method to calculate and justify their variance of returns in a particular portfolio.A high standard deviation of a portfolioStandard Deviation Of A PortfolioPortfolio standard deviation refers to the portfolio volatility calculated based on three essential factors: the standard deviation of each of the assets present in the total portfolio, the respective weight of that individual asset, and the correlation between each pair of assets of the portfolio.read more signifies a large variance in a given number of stocks in a particular portfolio. On the other hand, a low standard deviation signifies less stock variance among themselves.A risk-averse investor will only be willing to take any additional risk if they compensate by an equal or a larger return to take that particular risk.A more risk-averse investor may not be comfortable with his standard deviation. As a result, they would want to add safer investments, such as government bonds or large-cap stocksLarge-cap StocksLarge-cap stocks refer to stocks of large companies with value, also known as the market capitalization of 10 billion dollars or more, and these stocks are less risky than others and are stable. They also pay a good dividend and return, and it is the safest option to invest.read more in the portfolio or mutual funds, to diversify the portfolio’s risk and its standard deviation and variance.The variance and the closely-related standard deviation measure how spread out a distribution is. In other words, they are measures of variability.

Steps to Calculate Standard Deviation

Examples

Example 1

The data points are 1,2, and 3. What is the standard deviation of the given data set?

  • First, the mean of the observations is calculated just like the average adding all the data points available in a data set and dividing it by the number of observations. Then, the variance from each data point measures the mean. It can come as a positive or negative number, the value is squared, and the result is subtracted by one. The square of the variance calculated from Step 2 is taken to calculate the standard deviation.

Solution:

Use the following data for the calculation of the standard deviation.

So, the calculation of variance will be –

Variance = 0.67

The calculation of standard deviation will be –

Standard Deviation = 0.82

Example #2

Find the standard deviation of 4,9,11,12,17,5,8,12,14.

The calculation of the mean will be –

First, find the mean of the data point 4+9+11+12+17+5+8+12+14/9

Mean = 10.22

The variance will be –

Variance = 15.51

Standard Deviation = 3.94

Variance = Square rootSquare RootThe Square Root function is an arithmetic function built into Excel that is used to determine the square root of a given number. To use this function, type the term =SQRT and hit the tab key, which will bring up the SQRT function. Moreover, this function accepts a single argument.read more of standard deviation.

Example #3

Variance = 132.20

Standard Deviation = 11.50

Portfolio managers frequently use this type of calculation to calculate the risk and return of the portfolio.

Relevance and Uses

  • Standard deviation is historically helpful in analyzing a portfolio matrix’s overall risk and return. It is widely used and practiced in the industry. The correlation and the weights of the portfolio’s stocks can impact the portfolio’s standard deviation.As the correlation of the two asset classesAsset ClassesAssets are classified into various classes based on their type, purpose, or the basis of return or markets. Fixed assets, equity (equity investments, equity-linked savings schemes), real estate, commodities (gold, silver, bronze), cash and cash equivalents, derivatives (equity, bonds, debt), and alternative investments such as hedge funds and bitcoins are examples.read more in a portfolio reduces the portfolio’s risk, it is not necessary all the time that an equally weighted portfolio provides the least risk in the universe.A high standard deviation may be a measure of volatility, but it does not necessarily mean that such a fund is worse than one with a low standard deviation. For example, if the first fund is a much higher performer than the second one, the deviation will not matter much.Standard deviation is also used in statisticsStatisticsStatistics is the science behind identifying, collecting, organizing and summarizing, analyzing, interpreting, and finally, presenting such data, either qualitative or quantitative, which helps make better and effective decisions with relevance.read more and is widely taught by professors at various top universities worldwide. However, the formula for standard deviation is changed when one uses it to calculate the sample’s deviation.The equation for SD in Sample = just the denominator is reduced by 1.

This article is a guide to the Standard Deviation Formula. Here, we learn how to calculate standard deviation using its formula, practical examples, and a downloadable Excel template. You can learn more about financial modeling from the following articles: –

  • The equation for SD in Sample = just the denominator is reduced by 1.

  • Examples of the CorrelationStandard Deviation Excel FormulaStandard Deviation Excel FormulaThe standard deviation shows the variability of the data values from the mean (average). In Excel, the STDEV and STDEV.S calculate sample standard deviation while STDEVP and STDEV.P calculate population standard deviation. STDEV is available in Excel 2007 and the previous versions. However, STDEV.P and STDEV.S are only available in Excel 2010 and subsequent versions.

  • read moreFormula of Sample Standard DeviationFormula Of Sample Standard DeviationSample standard deviation refers to the statistical metric that is used to measure the extent by which a random variable diverges from the mean of the sample.read moreFormula of Relative Standard DeviationFormula Of Relative Standard DeviationRelative Standard Deviation (RSD) measures the deviation of a set of numbers disseminated around the mean and is calculated as the ratio of standard deviation to the mean for a group of numbers. The higher the deviation, the further the numbers are from the mean. The lower the deviation, the closer the numbers are to the mean.read more