Table 8. Kruskal-Wallis H test on different missing ring ratio events during 1200–2011.

MRR(%)	N	Mean Rank				Chi-Square	Asymp.Sig.(2-tailed)
		H	MH	ML	L
>10	13	34.77	28	18.46	24.77	7.826	0.05*
10-2	31	58.03	59.27	57.98	74.71	4.847	0.183
<2	105	208.6	236.82	202.18	194.4	10.435	0.015*
All	149	293.11	315.06	289.29	296.54	2.29	0.515

MRR: missing ring ratio; N: number of events; Mean Rank of H/MH/ML/L: mean ranks within each altitude belt; Chi-Square: Chi-Square coefficient; Asymp. Sig.: asymptotic significance, which means that the significance is very close to 0.

^*the value is significant at the p = 0.05 level.