What is the standard deviation of Q, a set of consecutive integers?
I) Q has 21 members
II) The median value of set Q is 20
Looking at the formula to calculate SD, Av = 10th number.
Therefore, the dfferences are 10, 9, 8, .., 0, ... -8, -10. (note that this is standard)
Since the magnitude of the numbers does not enter the calculation anymore, the SD is independent of what numbers are chosen, as long as they're consecutive 21 numbers. Sufficient.
(II) This doesn't tell us the dispersion of individual data, and hence unable to calculate SD with certainly. Insufficient.
Who says elephants can't dance?