Figure 1:
Illustration of hypothesis testing the effect of a treatment on nematode survival rate (A) and two types of errors that could occur (B). Figure created with Biorender.com.
Figure 2:
(A) Comparison of H. schachtii female counts per plant on wild-type (Col-0) and a DNA methylation-deficient triple mutant (drm1 drm2 kyp) A. thaliana (Ko et al., 2024) (Col-0: n = 31; drm1 drm2 kyp: n = 19). The group differences were assessed with a two-sided Wilcoxon rank-sum test. The effect size (Hedges’ g corrected) is 1.23. (B) Demo dataset created by randomly selecting five observations per group (n = 5) from Figure 2A. Two-tails Student t-test indicated a significant difference between two groups. (C) Ten simulated experiments, each with n = 5 per group, subsampled from the (Fig. 2A) dataset. Using a two-tailed Student’s t-test, statistically significant differences were observed in around 31% of simulations (orange panels). Open circles denote individual plants. The box-and-whisker plots show the median and interquartile range; whiskers indicate the full data range (min–max). Each point denotes one infected plant. Asterisks denote the group differences (*P < 0.05, ***P < 0.001).
Figure 3:
Ten simulated experiments, each with n = 10 per group, subsampled from the (Fig. 2) dataset. Open circles denote individual plants. Using a two-tailed Student’s t-test, statistically significant differences (marked with asterisks) were observed in around 70% of simulations (orange panels; *P < 0.05, **P < 0.01, ***P < 0.001).
Figure 4:
Nomogram for Cohen’s d effect size and power for comparing two groups of equal size using a two-sample t-test. Normal distributions and equal variance are assumed. Each curve represents a specific power at a significance value of α = 0.05 with a sample size on the x-axis and Cohen’s d effect size on the y-axis. In the example shown in Figure 3, for an experiment that has an effect size of 1.51 with a desire power of 0.8, the suggested sample size is about eight per group.
Figure S1:
Nomogram for η2 (Eta square) effect size and power for comparing: (A) three groups, (B) four groups, and (C) five groups of equal size using one-way ANOVA test. Normal distributions and equal variance are assumed. Each curve represents a specific power at a significance value of α = 0.05 with a sample size on the x-axis and η2 effect size on the y-axis. ANOVA, analysis of variance.
Figure S2:
Comparison of H. schachtii female counts per plant on wild-type A. thaliana (Col-0) and a DNA methylation-deficient triple mutant (drm1 drm2 kyp). Center lines show the medians; box limits indicate the 25th and 75th percentiles; whiskers extend 1.5 times the interquartile range from the 25th and 75th percentiles; crosses represent sample means; bars indicate 90% confidence intervals of the means; data points are plotted as open circles. n = 10 sample points. Asterisks denote the group differences assessed with a two-tailed Student’s t-test (***P < 0.001). The standardized effect size (Cohen’s d) is 1.52. Figure made with http://shiny.chemgrid.org/boxplotr/ (Spitzer et al., 2014).
Table S1:
Descriptive statistics shown in Figure S2 in Supplementary Material
| Sample size (N) | Mean (X) | SD | |
|---|---|---|---|
| Col-0 wild type (w) | 10 | 12.3 | 5.56 |
| Drm1drm2kyp mutant (m) | 10 | 26.9 | 12.36 |
Figure S3:
User interface of G*Power while conducting the power analysis of demo data.