4: Trong kì thi học sinh giỏi lớp 7, điểm số được ghi lại như sau (thang điểm 100) 17 40 33 97 73 89 45 44 43 73 58 60 10 99 56 96 45 56 10 60 39 89 56 68 55 88 75 59 37 10 43 96 25 56 31 49 88 23 39 34 38 66 96 10 37 49 56 56 56 55 1) Dấu hiệu cần tìm hiểu ở đây là gì? 2) Lập bảng ”Tần số”. 3) Tính điểm trung bình của các HS dự thi và tìm mốt của dấu hiệu. 3) Để đủ điều kiện xếp giải HS phải đạt trên 50% yêu cầu của bài thi, vậy có bao nhiêu HS đạt giải trong kì thi đó? 4) Các HS đạt từ 88 điểm trở lên được chọn vào đội tuyển của trường. Vậy đội tuyển đó có bao nhiêu người?

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