A study of the precision of the semiempirical methods used in the determination of the chemical abundances in gas-rich galaxies is carried out .
In order to do this the oxygen abundances of a total of 438 galaxies were determined using the electronic temperature , the R _ { 23 } and the P methods .
The new calibration of the P method gives the smaller dispersion for the low and high metallicity regions , while the best numbers in the turnaround region are given by the R _ { 23 } method .
We also found that the dispersion correlates with the metallicity .
Finally , it can be said that all the semiempirical methods studied here are quite insensitive to metallicity with a value of 8.0 \pm 0.2 dex for more than 50 \% of the total sample .