Analysis of Variance
Analysis of Variance is used in comparing more than two sample groups.
One very important statistical method for microbiologists to understand is Analysis of Variance (ANOVA). In its most basic form, it is but an extension of two-sample testing that includes testing of more than two sample groups. For example, there may be four sample groups in a study to compare or three media types to contrast. The main difference from our previous work is that ANOVA uses variances, s2, as its prime measurement and the standard deviation, s. The F distribution used in ANOVA is just the t-tabled value squared. A tt tabled value of 1.96, when computing two samples in the F distribution is F = 3.84, which is t2.
The general statistical rationale behind ANOVA lies in the comparison of two variances: the variance between the treatments and the variance within the treatments. If the between- and within-variances are equal, then no treatment effect is present. ANOVA variances are calculated by...