Question

Standard deviation can be used when *
1..The measure of central tendency is available in the form of median
2. .We need a most reliable measure of variability
3..It is needed to weigh all deviations from the mean according to their size​

Answer 1

The mean is usually the best measure of central tendency to use when your data distribution is continuous and symmetrical, such as when your data is normally distributed. However, it all depends on what you are trying to show from your data.

hope its helps you to understand