Question

这是一道统计学的英文数学题，请帮我解释一下问题的意思，因为我真的看不懂

Instead of wanting to know what percent of the data falls into a particular class, we often want to
know what percent falls below a certain value. To make this possible, we will compute the
cumulative relative frequency for each class, which is the sum of the relative frequency of that class
and all the classes below it.

Exam Score frequency relative freq. cumulative r.f.
0-<10 2 0.01 0.01
10-<20 7 0.035 0.045
20-<30 9 0.045
30-<40 12
40-<50 23
50-<60 34
60-<70 48
70-<80 39
80-<90 19
90-<100 7
total 200

Consider the following frequency distribution of 200 Algebra 1 final exam scores. Complete the
cumulative relative frequency table and use it to respond to the questions that follow:
(a) What proportion of students scored less than 30? less than 90?
(b) What proportion of students scored at least 40? at least 70?
(c) What proportion scored exactly 40? exactly 73?
(d) What proportion scored at least 50 but less than 70?

Answer 1

proportion是比例，第一题问少于30的比例和少于90的比例，看数据就知道（90~100那里有7个，占7/200的比例）
第二题，大于等于40分的比例，大于等于70的比例
第三题不懂
第四题少于70大于等于50的比例