一个统计问题,英文,看不懂什么叫missed and created的意思!

一个统计问题,英文,看不懂什么叫missed and created的意思!
An instructor is evaluating the performance of students on a test.He records the number of points that each student missed and created a frequency distribution.This is provided below:
Points missed Number of students
0-under 10 2
10-under 20 4
20-under 30 10
30-under 40 8
40-under 50 6
What is the mean number of points missed?
希望能帮我解决!