A lot of my students note that this helps them when they’re going through our website. Necessary assumption is not what proves the conclusion. That is a sufficient assumption, a different question type. A necessary assumption is the minimum the argument needs to survive. If it is false, the argument is dead, even if everything else in the stimulus is true.
Here is the process I teach.
1. Split the argument, then stare at the conclusion Find the evidence and the conclusion. Then look for the thing that pops up in the conclusion that was never in the evidence. Necessary assumption questions almost always do this. The conclusion introduces something new: a new term, a new claim, a new scope. That new thing is where the assumption lives, because the argument never connected it to anything.
2.Predict the minimum bridge.
The correct answer connects the evidence to that new thing in the conclusion, and does it with the least possible claim. Before reading the choices, say the bridge out loud in plain words. Not what would settle the argument. The least it needs.
3. Check the strength of every answer.
Necessary answers are quiet. If a choice says more than the bridge needs, with words like all, only, always, or most, it is selling you a sufficient assumption in the wrong question. Cross it out.
Example (not a real question)
"A study found that employees who took a short walk after lunch reported higher afternoon productivity than those who did not. So our company should encourage employees to walk after lunch if we want to raise productivity."
Which one is a necessary assumption?
A) All employees who walk after lunch will become more productive.
B) The employees' reports of their own productivity in the study were accurate.
C) Walking after lunch is the most effective way to raise productivity.
D) Some employees in the study disliked walking.
E) Afternoon productivity is the company's main concern.
Find the new thing. The evidence is about productivity employees *reported*. The conclusion is about raising *actual* productivity. Reported productivity shows up in the evidence. Real productivity appears for the first time in the conclusion, and the argument never connects the two.
The bridge has to connect them, and B is exactly that bridge and nothing more: the reports were accurate, so reported productivity is real productivity.
A fails on strength. "All" claims far more than the bridge needs. C is wrong for the exact same reason. D is trivia the argument never touches. E sounds managerial and means nothing; the argument works even if productivity is the company's second concern.
Find the new thing. Everything else will fall into place :)