Morris High School has introduced a policy designed to improve the working conditions of its new teachers.
Conclusion (Thus)
More full-time than part-time teachers at Morris now quit during their first year.
Evidence
One-quarter of part-time teachers quit in their first year.
One-third of full-time teachers quit in their first year.
Evaluate
The evidence gives fractions. The conclusion gives a comparison of numbers: more full-time teachers quit than part-time teachers.
Any time we're doing Flaw and we see a switch from relative ideas (percent / fraction) to absolute ideas (number / amount), we want to suspect the % vs. # flaw.
This is when authors imagine that a bigger percentage/fraction automatically means a bigger number.
1/3 is bigger than 1/4, so the author thinks the former quantity is bigger.
But to turn a fraction / percentage into a number, you need to apply it to a group. A third of a small group can be fewer people than a quarter of a large one.
If Morris employs 30 new full-time teachers and 120 new part-time teachers, a third of the first is 10 and a quarter of the second is 30, and more part-time teachers quit.
The argument would hold only if the two groups were about the same size or the full-time group were larger, which it never says.
Goal
This is the Famous Flaw of Relative vs. Absolute: a bigger percentage is taken to mean a bigger number.
Since the answers are all prefaced by fails to consider / ignores the possibility, we'll treat them all like Weaken answers.
Look for one saying that there could be way more part-time teachers than full time teachers (and thus there could be more part-timers quitting during first year).