Standard Deviation (SD)

<a href="https://www.prepswift.com/quizzes/quiz/prepswift-standard-deviation-sd" target="_blank">Standard Deviation (SD) Exercise</a>Standard Deviation is a value that gives us an idea of how "spread out" a group of numbers is. The higher the standard deviation, the greater the spread. A couple of points before we dive into standard deviation in more detail in future mountain entries. Point 1: Standard deviation is represented by $\sigma$. $$standard \ deviation = \sigma$$ Point 2: Standard deviation is never negative. It's greater than or equal to $0$. $$\sigma \geq 0$$ Point 3: To really drive home the fact that standard deviation can never be negative, even a list of negative numbers like $-11, -5, -1$ has a positive standard deviation. Point 4: Teachers who struggle to write the $\sigma$ symbol often substitute $sd$ or $std$. Point 5: Why do researchers and math people even care about standard deviation? Because it gives information that other numbers just don't. For example, imagine someone is shooting arrows at a target and receives the following scores: $$77, 81, 82, 80$$ The average and the median are both around $80$ in this case, but those numbers don't tell us how ACCURATE this archer is. Because the numbers are so close together, the standard deviation will be low, and we'll know that this is an accurate archer. Vice versa, if the standard deviation were high, we would know that this archer is inconsistent and "all over the place."