Table 2.

Repeated measures analysis of variance results for volumes of corn lower- and upper-root systems and the two combined.

Source	df	Lower roots	Upper roots	Lower and upper roots combined
		P-value
Group† (in Week 1)	1	0.3290§	N/A‡	0.1822
Group† (in Week 2)	1	0.2849	0.1073	0.1494
Group† (in Week 3)	1	0.0870	0.0800	0.0803
Between-subject effects
Group	1	0.1956	0.0908	0.1136
Error	4
Within-subject effects
Week	2‡	<0.0001	0.0093	0.0016
Week × Group	2	0.0041	0.0543	0.0759
Error (Week)	8

^†Except for N/A, the Error df is 4 (df: number of degrees of freedom).

^‡Corn plants of the salt-stressed group had no upper root in Week 1. It follows: (i) the non-relevance of performing a statistical test to compare groups for their upper-root volumes in Week 1; (ii) within-subject effects with 1, 1, and 4 df instead of 2, 2, and 8 df, due to the inclusion of 2 weeks (Weeks 2 and 3) instead of the 3 weeks in the ANOVAR for upper-root volume.

^§ 0.3776 if a t-test with an effective number of df is used, to adjust for the sole case of significant (P < 0.05) between-group heterogeneity of the variance in our study.