90. Solving a chemistry problem

204. Find the standard deviation of a single determination and the confidence interval of the mean value (for p = 0.95):
204. During volumetric titration with an alkali solution of a reaction mass containing phenol and acetone, the following results were obtained (in%);
for phenol: (55.27; 56.40; 56.15; 55.80; 57.00; 55.90);
for acetone: (33.23; 34.10; 33.80; 34.00; 34.25; 33.50).