# How to use Standard Deviation to support investment decision making

Standard deviation is a statistical measure that is used to quantify the dispersion or variability of a set of data points from the mean. In finance, standard deviation is a widely used tool that investors use to analyze the risk associated with various investments. It serves as a valuable tool in helping investors make informed decisions about their investments.

In this article, we will explore how investors can use standard deviation to support decision-making in their investment strategies. We will discuss what standard deviation is, how it is calculated, and how it can be used to assess investment risk.

**What is Standard Deviation?**

Standard deviation is a statistical measure that reflects the amount of variation or dispersion in a set of data points relative to the mean. It is a measure of how spread out the data is from the average. The larger the standard deviation, the more spread out the data is, while the smaller the standard deviation, the more tightly clustered the data is around the mean.

The formula for standard deviation is:

σ = √(∑(xi-μ)²/N)

Where:

σ = standard deviation

xi = each data point

μ = mean of the data set

N = number of data points

In finance, standard deviation is used as a measure of risk. Investors use it to assess the degree of variability or volatility in an investment's returns. The higher the standard deviation, the riskier the investment is considered to be.

**How is Standard Deviation Used in Investing?**

Investors use standard deviation in several ways to support their decision-making process. Here are some of the ways investors use standard deviation in investing:

**1. To measure the risk of an investment**

The primary use of standard deviation in investing is to measure the risk associated with an investment. Standard deviation is a useful tool for assessing how much an investment's returns are likely to deviate from its expected returns. The higher the standard deviation, the greater the risk associated with the investment.

For example, let's say an investor is considering investing in two different stocks. Stock A has an average annual return of 10% with a standard deviation of 5%, while Stock B has an average annual return of 10% with a standard deviation of 15%. The higher standard deviation of Stock B indicates that its returns are more volatile and unpredictable, making it a riskier investment than Stock A.

**2. To compare the risk of different investments**

Investors can also use standard deviation to compare the risk of different investments. By comparing the standard deviation of different investments, investors can determine which investment is riskier and which one is less risky.

For example, an investor may be considering investing in two mutual funds. Mutual Fund A has an average annual return of 8% with a standard deviation of 12%, while Mutual Fund B has an average annual return of 8% with a standard deviation of 8%. The lower standard deviation of Mutual Fund B indicates that it is less risky than Mutual Fund A.

**3. To determine the appropriate asset allocation**

Asset allocation is an investment strategy that involves diversifying an investor's portfolio by investing in a mix of different asset classes, such as stocks, bonds, and cash. Investors can use standard deviation to determine the appropriate asset allocation for their portfolio.

For example, if an investor has a low tolerance for risk, they may want to invest in assets with lower standard deviations, such as bonds and cash, which are less volatile than stocks. On the other hand, if an investor has a high tolerance for risk, they may want to invest in assets with higher standard deviations, such as stocks, which have the potential for higher returns but also greater volatility.

**4. To assess the performance of a portfolio**

Investors can also use standard deviation to assess the performance of their portfolio. By calculating the standard deviation of their portfolio's returns, investors can determine how much their portfolio's returns have deviated from their expected returns.

For example, if an investor's portfolio has an average annual return of 7% with a standard deviation of 10%, they can determine that their portfolio's returns have deviated from the expected return by up to 10%. This information can be used to adjust the portfolio's asset allocation or to make other investment decisions.

**Conclusion**

Standard deviation is a powerful tool that investors can use to support their decision-making process. It is a valuable measure of risk that can be used to assess the variability or volatility of an investment's returns. By using standard deviation, investors can measure the risk of an investment, compare the risk of different investments, determine the appropriate asset allocation, and assess the performance of their portfolio. With this information, investors can make informed decisions that align with their investment goals and risk tolerance.