significance level threshold? 这个是arbitrarily defined at .05 (5%)。analysis的结果小于.05就是significant。大概意思就是弄错的可能性很小。
如果是问什么test,原来的article写的很清楚。univariate ANOVA yielded a significant effect of age. then t-tested were done within these age groups to find out the direct of difference and where the difference lies in.