Deviations from the mean sum to zero. Use the definition
Chapter , Problem 1.94(choose chapter or problem)
Deviations from the mean sum to zero. Use the definition of the mean x to show that the sum of the deviations xi x of the observations from their mean is always zero. This is one reason why the variance and standard deviation use squared deviations.
Unfortunately, we don't have that question answered yet. But you can get it answered in just 5 hours by Logging in or Becoming a subscriber.
Becoming a subscriber
Or look for another answer