Comparisons of the 3 treatment zone diameters and the volume between the five treatment groups are summarized in Table 1, where the \(p\)-values are based on the nonparametric kruskal-Wallis test (with 4 degrees of freedom).

Table 1. Measurement mean (SD) by treatment group.
0 cm, voltage 0 cm 1 cm 2 cm Control p-value
Z 2.52 (0.29) 2.2 (0.23) 2.23 (0.26) 2.12 (0.27) 1.85 (0.08) 0.003
X 2.43 (0.1) 2.48 (0.04) 2.2 (0.23) 2.42 (0.08) 2.35 (0.14) 0.045
Y 2.6 (0.25) 2.62 (0.17) 2.53 (0.16) 2.47 (0.16) 2.28 (0.08) 0.016
Volume 8.41 (1.78) 7.51 (1.12) 6.55 (1.33) 6.68 (1.44) 5.2 (0.37) 0.005

Boxplots of the measurements by treatment group are shown below. The calculated volumes in each group are compared with the prescribed 8.2 using the one-sample \(t\)-test on their differences.

Table 2 below tabulates the \(p\)-values from Tukey’s pairwise comparison of means between the 5 groups.

Table 2. P-values of Tukey’s pairwise tests of means.
0 vs 0-volt 1 vs 0-volt 2 vs 0-volt Ctr vs 0-volt 1 vs 0 2 vs 0 Ctr vs 0 2 vs 1 Ctr vs 1 Ctr vs 2
Z 0.179 0.270 0.054 0.001 0.999 0.973 0.114 0.913 0.070 0.326
X 0.965 0.041 0.999 0.814 0.009 0.907 0.434 0.065 0.320 0.907
Y 1.000 0.963 0.681 0.032 0.920 0.580 0.022 0.963 0.128 0.386
Volume 0.751 0.126 0.174 0.002 0.703 0.798 0.036 1.000 0.393 0.306

Overall comparison with prescribed

We combine all diameters (x, y, and z) for each and all bowel groups (0 cm voltage, 0 cm, 1 cm, and 2 cm) as well as the control, and compare them with the prescribed diameter of 2.5 cm.

Table 3 below lists the mean (SD) for each group, with p-values for comparison with 2.5 cm using repeated measures (3 measures per unit) ANOVA.

Table 3. Comparison of all X, Y, and Z diameters to prescribed (2.5 cm).
Treat Mean (SD) P
All bowel 2.4 (0.25) 0.003
0 cm volt 2.52 (0.23) 0.82
0 cm 2.43 (0.24) 0.234
1 cm 2.32 (0.26) 0.003
2 cm 2.33 (0.24) 0.012
Control 2.16 (0.25) <0.001