Yuri computes the mean and standard deviation for the sample data set 12 , 14 , 9 , and 21 He finds the mean is 14 Yuri's Work s=sqrt(((12−14)^2+(14−14)^2+(9−14)^2+(21−14)^2)/(4)) is equal to square root of the fraction with numerator negative 2 squared plus 0 squared plus negative 5 squared plus 7 squared and denominator 4 end root is equal to square root of the fraction with numerator 4 plus 0 plus 25 plus 49 and denominator 4 end root is equal to square root of 78 fourths is equal to square root of 19 point 5 What is the first error he made in computing the standard deviation?