题目

某中学九年级举办中华优秀传统文化知识竞赛．用简单随机抽样的方法，从该年级全体600名学生中抽取20名，其竞赛成绩如图： （1） 求这20名学生成绩的众数，中位数和平均数； （2） 若规定成绩大于或等于90分为优秀等级，试估计该年级获优秀等级的学生人数． 答案：解：由列表中90分对应的人数最多，因此这组数据的众数应该是90， 由于人数总和是20人为偶数，将数据从小到大排列后，第10个和第11个数据都是90分，因此这组数据的中位数应该是90， 众数：90，中位数：90， 平均数 =80×2+85×3+90×8+95×5+100×220=90.5 ． 答：这20名学生成绩的众数90，中位数90，和平均数90.5根据短文内容，判断正(T)误(F)。     There are eighteen boys and twenty-five girls in our class. One of the boys is English. His name is Tom. He is thirteen. Two of the girls are American. They are twins. Their names are Jane and Joan. They are twelve. They are my friends. All of the Chinese boys and girls are Young Pioneers (少先队员). We all Chinese students like (喜欢) the English boy and the American girls, and they like us, too. We help each other.(     )1. In our class there are forty-three students.(     )2. The twin sisters are from England.(     )3. Joan is twelve, and Tom is thirteen.(     )4. All the students in our class are Young Pioneers.(     )5. We like American and English students.