By using the definition of "standard deviation". If is the mean, the standard deviation is
The paper referenced in Exercise 4.25 also gave summary quantities for sodium content (in milligrams per kilogram) of chocolate pudding made from instant mix:
a. Compute the mean, the standard deviation, and the interquartile range for sodium content of these chocolate puddings.
I can compute the mean and the interquartile range but how do you find the standard deviation?