Table 1.

The descriptive statistics of PM_2.5 (μg/m³).

city	Chongqing	Chengdu	Zigong	Luzhou	Deyang	Mianyang	Suining	Neijiang
Mean	38.15	49.44	52.60	37.75	41.62	45.34	34.85	37.25
S.D.	21.25	32.16	36.04	26.51	31.27	32.84	21.22	27.60
skewness	2.02	1.42	1.43	1.58	1.56	1.68	1.69	1.34
kurtosis	5.62	2.69	2.33	2.69	3.11	4.01	5.74	1.89
PP test	−6.37***	−6.61***	−5.23***	−5.95***	−6.28***	−5.77***	−6.62***	−5.22***
city	Leshan	Nanchong	Meishan	Yibin	Guang’an	Dazhou	Ya’an	Ziyang
Mean	45.92	46.83	38.48	50.68	40.32	45.84	39.56	34.73
S.D.	28.48	24.29	25.67	30.55	26.08	32.70	27.59	24.02
skewness	1.34	1.40	1.56	1.24	1.71	1.87	1.30	1.68
kurtosis	2.34	3.03	3.13	1.43	4.21	4.35	1.98	2.66
PP test	−6.99***	−6.59***	−6.38***	−6.83***	−6.39***	−6.31***	−6.53***	−4.82***

Notes:*Significance at 10% level; **Significance at 5% level; ***Significance at 1% level.