Question

Molarity of standardized NaOH solution is 0.1012
final buret reading, mL IS 31.21
INITIAL buret reading, mL IS 15.72
VOLUME OF TITRANT, mL is 15.49
Moles of NaOH used is 1.568*10^-3 mol
Moles of HC2H302 neutralized by the NaOH is 1.568*10^-3 Mol
Molarity of dill HC2H302 is .0783
avearge molarity of diluted vinegar is 0.7865 M
the deviation di is .000350

How do i calculate the average deviation, D

±∑??(x1−xave)/n