题干

某校九年级200名学生在第一学期的期末考试中数学成绩(分数都是整数)分布如表:

分数段

75~89

90~104

105~119

120~134

135~149

频率

0.1

0.15

0.25

0.35

0.15

表中每组数据含最小值和最大值,在最低分为75分与最高分为149分之间的每个分数都有学生,那么下列关于这200名学生成绩的说法中一定正确的是(  )

A:中位数在105~119分数段

B:中位数是119.5分

C:中位数在120~134分数段 

D:众数在120~134分数段

上一题 下一题 0.0难度 选择题 更新时间:2018-02-15 01:26:34

答案(点此获取答案解析)

B

同类题3

阅读理解

    If you want to live longer and lower the risk of heart disease, a move to the mountains may help. Research by scientists in Greece shows that living in the mountains is good for the heart and longevity(长寿). People living at higher altitude(海拔) have lower possibility of dying from heart disease than those closer to sea level, even if they have factors that could increase their risk. "Residence in mountainous areas seems to have a 'protective effect' from heart disease," said Dr Nikos Baibas of the University of Athens. He and his colleagues suspect that the increased exercise from walking up mountainous area gives the heart a good workout and enables it to cope with lower levels of oxygen.

    Researchers studied the health records and death rates of 1,150 Greeks who lived in three villages near Athens over 15 years. One village was 1,000 meters above sea level and the other two were in low-lying areas. Although men and women living in the mountainous village had higher blood pressure rates and other risk factors than people in the other villages, they had a lower rate of death from heart disease and other causes after a fifteen year follow-up." The contrast was more evident among men than among women," Baibas added in a report in the Journal of Epidemiology and Community Health. Heart disease is one of the world's top killers. Smoking, high blood pressure, raised cholesterol levels, being overweight and a family history of the illness increase the possibility of developing the disease.