The document provides data on the Most Probable Number (MPN) index and 95% confidence limits for determining bacterial density in drinking water using two different sampling techniques. It includes tables detailing positive reactions for various combinations of tube results when using five 20 ml portions and ten 10 ml portions. The source of the methods is referenced as Standard Methods 9221 B from June 2003.

1. TABLAS DE NMP PARA AGUA POTABLE
9221 C. ESTIMACIÓN DE LA DENSIDAD BACTERIANA
TABLA 9221: II MPN Index and 95% Confidence Limits for All Combinations of Positive and
Negative Result when five 20 ml portions are used.
No. Of tubes giving MPN Index/100ml 95% Confidence Limits
positive reaction out (Exact)
of 5 (20 ml each) Lower Uper
0 <1.1 - 3.5
1 1.1 0.051 5.4
2 2.6 0.40 8.4
3 4.6 1.0 13
4 8.0 2.1 23
5 >8.0 3.4 -
TABLA 9221: II MPN Index and 95% Confidence Limits for All Combinations of Positive and
Negative Result when ten 10 ml portions are used.
No. Of tubes giving MPN Index/100ml 95% Confidence Limits
positive reaction out (Exact)
of 10 (10 ml each) Lower Uper
0 <1.1 - 3.4
1 1.1 0.051 5.9
2 2.2 0.37 8.2
3 3.6 0.91 9.7
4 5.1 1.6 13
5 6.9 2.5 15
6 9.2 3.3 19
7 12 4.8 24
8 16 5.8 34
9 23 8.1 53
10 >23 13 -
Fuente: STANDARD METHODS 9221 B. STANDARD TOTAL COLIFORM FERMENTATION TECHNIQUE , JUNE
2003