Table 3. Principal component analysis (PCA) of sAUDPS indexes of all testing sites.

SOV	Contributing rate (%)	df	Sum of Squares	Mean Square	F-value	P-value
IPCA1	42.60	183	144.33	0.79	6.02**	0.00E+00
IPCA2	28.30	181	95.88	0.53	4.04**	0.00E+00
IPCA3	21.60	179	73.13	0.41	3.12**	0.00E+00
IPCA4	7.40	177	25.20	0.14	1.09	0.2051

Notes:

df: degree of freedom.

^**Represent significance at 0.01 levels (p < 0.01).