points one student got 1 分,2分,3分,4分
问题描述：
points one student got 1 分,2分,3分,4分
number of students 4 人 7人 8人 6人（上下对应,即拿了1分的学生有4个）
1what is the median points?
2 if the teacher chooses one of her students at random,what is the probability that that student will have earned higher than the median grade on the quiz?
(我搞不懂这里的higher than median到底包不包括median自身)
答
1,1,1,1,2,2,2,2,2,2,2,3, 3, 3,3,3,3,3,3,4,4,4,4,4,4
中间数是 3
median = 3
higher than median 不包括 median 本身
总人数是25
六个人大於 median
6/25
例题 2,2,3,4,5,6 的median 是 (3 + 4)/2 = 3.5