A friend of mine work it out for me,it's 1/6,I am not sure.I wonder why don't you ask the question in Chinese.Okay,I'll translate it into Chinese for you and someone who good at math but English.
调查显示,徒步穿越一个特殊的国家公园一般需要3.6h,此结果有0.5h的误差.计算随机挑选一个徒步者其穿越该公园耗时低于3h的概率.