The Evaluation of the Bactericidal Activity of Ethylene Glycol and Some of its Monoalkyl Ethers Against Bacterium Coli: Part Vi

Abstract

Summary The course of the disinfection (at 20°C) between Bact. coli and several concentrations of the following ethers of ethylene glycol has been investigated: monomethyl, monoethyl, monopropyl, monobutyl and monohexyl. Several experiments were conducted at every concentration and probit-log. time regressions calculated for all experiments. For every concentration of a substance the sum of squares for the common regression and for the variation in regression was calculated; the error mean square of the regression was also computed. The data for every concentration of each compound have been pooled, and a mean regression has been calculated for each compound. The statistical data from all the calculations for the terms of the regressions for every concentration of the compounds (at 20°C) have been massed and an analysis of variance carried out. The probabilities for the differences between the mean squares of the items in the analysis of variance have been deduced by means of the z distribution. No significant difference could be shown between the variation in regression between concentrations and between tests; these two errors have been pooled in order to establish the error mean square for all the estimations performed. The probit-log. time regression coefficient for every compound has been compared with its standard error; in all cases the ratio was large thereby indicating that b had been estimated satisfactorily. Confidence limits (at P = 0ṁ05) of the probit-log. time regressions have been calculated and a diagram constructed to show the increased precision obtained when many tests are performed at the same concentration.