F might mean one kind of statistical test: ANOVA test. The two parameters in F( , ) are degrees of freedom required to calculate F statistic. I don't think the author uses the number of percentage to get the result, i.e. F(1, 343) = 106.
对来自不同组别的两个比例进行比较可以依据Woods, Fletcher & Hughes(2000:182-184)的方法,先用公式计算出Z值,然后将其与临界值(1.960)进行比较来判断差异的显著性(如果Z值大于临界值,则差异显著(P < .05);反之差异不显著。)。文献信息:Woods, A., P. Fletcher & A. Hughes. 1986/2000. Statistics in Language Studies [M]. Beijing: Foreign Language Teaching and Research Press.