在评估水系统微生物监测的发生频率方法时，比较了克拉克有无（P-A）试验与膜过滤（MF）技术的有效性。结果显示，两种方法检测出的阳性组分之间没有显著差异。通过P-A试验和MF方法以相同的频率检测水的微生物质量的主要变化，通过出现频率参数比通过平均MF大肠菌群计数更容易检测到。包括9个参考文献和表格。

The effectiveness of Clark's presence-absence (P-A) test was compared with that of the membrane filter (MF) technique during an evaluation of the frequency-of-occurrence approach to microbiological monitoring of water systems. Results showed no significant difference between the fractions that were positive by the two methods. Major changes in the microbiological quality of the water were detected with equal frequency by the P-A test and the MF method and were detected more readily by the frequency-of-occurrence parameter than by the average MF coliform count. Includes 9 references, tables.