Calibration of a 50 ml buret

Question

(10 ml,15 ml,20ml,
25 ml,30ml,35ml,40ml,45ml,50ml)(repeated the procedure 3 times)
for experimental ; i have observed vol(ml) , temp.C ,for true i have mass(g), true vol. ml and for calibration i found error ml /correction ml(for each one)

i have the mean observed volume for each group of 3 and as well as mean corrected volume for each group of 3 )
also i found average temp and water density at this temp.

so my question is below
show a calculation for the total uncertainty in a volume read from your buret . This will require you to use propagation of error.

and identify one possible source of error in this calibration (not "human error")