TABLE 4.

Likelihood-ratio test (LRT) of positive selection under site models for ORF6 (n = 18).

Model comparison	Log-likelihood (lnL)	Free parameters	df	2ΔlnL	p − value
M1a vs. M0	lnL 1a = −353.034222, lnL 0 = −359.202823	336 vs. 335	1	12.337	0.000444
M3a vs. M0	lnL 3a = −348.06440, lnL 0 = −359.202823	339 vs. 335	4	22.277	0.0001765
M2a vs. M1a	lnL 2a = −348.064440, lnL 1a = −353.034222	338 vs. 336	2	9.9396	0.006945
M8 vs. M7	lnL 8 = −348.067766, lnL 7 = −353.199695	338 vs. 336	2	10.264	0.005905

M0 = one ratio.

M1a = nearly neutral.

M2a = positive selection.

M7 = beta.

M8 = beta and ω.

2ΔlnL = log-likelihood ratio test.

p − value = p − value of the chi-squared test.