The variance of a data set is 49. What is its standard deviation?

1. Variance is the average squared distance between the mean and each data value. 2. Because it is squared, it cannot be compared directly with the data or the mean. 3. The standard deviation fixes this, since it is the square root of the variance. 4. So take the square root of 49. 5. Seven times 7 is 49, so the square root of 49 is 7. 6. The standard deviation is therefore 7, and it carries the same units as the data. 7. Answering 2401 squares the variance instead of taking its root. 8. Answering 24.5 halves the variance, which is not the same as taking a square root. _Source: Siyavula Mathematics Grade 11 (Everything Maths, CC BY 4.0), Chapter 11: Statistics_