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】As a group, those persons who completed the course are more competent as mechanics than the group that did not.