The only way a set can have a SD of 0 is if all the terms are the same.resilient wrote:Set X consists of 8 integers. Is the standard deviation of set X equal to zero?
(1) The range of set X is equal to 3
(2) The mean of set X is equal to 5
(1) range is 3. Well, if range > 0, then some of the terms are different. Therefore, the set definitely does NOT have a SD of 0: sufficient.
(2) mean is 5. Set could be {5,5,5} (so YES, SD=0) or set could be {3,5,7} (so NO, SD not = 0): insufficient.
(1) is suff and (2) isn't: choose (A).
