Table 3.

ANOVA and variance components for I data^a

Expt no.	Variation source	SS	d.f.	MS	F	P	Explanation of variance (%)
1	tx	0.952	3	0.317	2.322	0.254	13.54 ± 0.39
	Ne	1.418	1	1.418	10.377	0.049	29.58 ± 1.04
	Ne×tx	0.410	3	0.137	6.139	0.001	23.05 ± 0.33
	Error	1.246	56	0.022			33.82 ± 0.03
2	Ne	1.143	9	0.127	3.713	0.003	33.41 ± 0.26
	Error	1.128	33	0.034			66.59 ± 0.13

^aTwo-way analysis of variance (ANOVA) on the data from the experiments measuring the proportion of infected cells in systemically infected tissue when both t_x and N_e were varied (experiment 1; see Fig. 6), and the proportion of infected cells in the systemically infected tissue when only N_e was varied (experiment 2; see Fig. 7). SS, sum of squares; d.f., degrees of freedom; MS, mean square. Explanation of variance is the percentage of variance explained by the model, which was estimated by a maximum likelihood-based variance components analysis in SPSS, and the asymptotic covariance is given as an indication of estimate error.