题目

(1)他们有相当宽松的规定。(pretty relaxing) (2)我们从未不提前打电话就拜访朋友家。(without)(3)作为一名学生，你应该努力学习。(be supposed to)(4)你若晚到一会儿也不要紧。(a bit late)(5)吃太多的油和盐对我们的健康不利。(eating) 答案：【1】They have pretty relaxing rules.【2】We never drop by a friend's home without calling first.【3】As a student, you are supposed to study hard.【4】It's OK if you arrive a bit late.【5】Eating too much oil and salt is bad for our health.总体的平均数、标准差可以通过________方法，用样本的平均数、标准差来估计它们.