The %RSD that we obtain from part of standardization of iodine solution with ascorbic acid is 1.792% which means it has high precision because the value of %RSD lower than 5%. Next, we used Thai Recommended Daily Intakes (%RDI) to compare with the average of concentration of ascorbic acid to find the percent error. The percent error that we obtain from the experiment of guava juice is 263.08% which means it have low accuracy because the value of percent error higher than 5%. We can’t find the percent error of concentration of ascorbic acid (in apple juice) because the label of product doesn’t show us the percent of vitamin C.