题目选项分析

Among those automobile mechanics who own their own garages and completed a qualifying course at Main Street Technical School, 35% earn above $80,000 a year. Among those who own their own garages but did not complete the qualifying course at Main Street Technical School, only 10% earn above $80,000 a year. These figures indicate the importance of technical education in getting a higher salary.

The argument above depends on which of the following assumptions about the people mentioned in the statistics?

【选项】The group of people who did not complete the qualifying course and the group who did are comparable in terms of factors that determine how much people are paid.