NewsBeat

September 2022 NewsBeat 16 By DENISE-MARIE ORDWAY What's standard deviation? Four things journalists covering research need to know If you're a journalist who reads academ- ic research, you've likely seen the term "standard deviation" many times. If you're not sure what it means or how to explain it to audiences, keep reading because we're going to break it down for you. Here are four key things you need to know: 1. The standard deviation of a dataset is a number that indicates how much variation there is within the data. When researchers analyze quantitative data such as birth rates, temperature read- ings and student test scores, they typically calculate the standard deviation of the data to gauge how close or far apart the data are. A higher standard deviation means the data are more spread out. The lower the standard deviation, the more closely data cluster around the average value of the data. Deborah J. Rumsey, a statistics professor at The Ohio State University, points out in her book Statistics for Dummies that the measure provides critical context. "Without it, you're getting only part of the story about the data," she writes. "Stat- isticians like to tell the story about the man who had one foot in a bucket of ice water and the other foot in a bucket of boiling water. He said on average he felt just great! But think about the variability in the two temperatures for each of his feet. Clos- er to home, the average house price, for example, tells you nothing about the range of house prices you may encounter when house-hunting. The average salary may not fully represent what's really going on in your company, if the salaries are extremely spread out." 2. Scientists can use standard deviation to make predictions, in- vestigate trends and answer other key research questions. The standard deviation of a dataset plays a limited role in many academic studies. Scientists might only note standard devi- ation values in a table or list or mention them within the body of an academic arti- cle. Sometimes, however, researchers rely heavily on the measure to help them an- swer questions central to their studies. For example: Researchers can make predictions about the weather, voter behavior, tax rev- enue, healthcare usage and a host of other things based partly on the standard devia- tion of data gathered over time. Equities researchers typically use the standard deviation of stock prices to mea- sure market volatility, with a high standard deviation indicating high volatility. Researchers examining student test scores can use the standard deviation to determine whether most students perform at or close to the average or whether test scores are all over the place. The measure also allows researchers to estimate the pro- portion of students who need more help mastering the material. 3. In some studies, scientists report their findings in terms of standard deviations instead of a unit of measurement such as inch- es or pounds. When datasets have data points with different units, scientists often need to standardize, or rescale, the data before they can draw comparisons and look for relationships. For instance, scientists might

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