Why do students confuse Inference and Assumption in CR?

As a teacher, I see this confusion all the time because both question types involve something that is not directly stated.

But the logic is very different.

Inference asks:
What follows from the information given?

Assumption asks:
What must be true for the argument to work?

That difference matters.

For an inference question, treat the statements as facts and ask:

“What can I safely conclude from these facts?”

You are moving forward from the evidence.

For an assumption question, first find the conclusion and ask:

“What is missing between the evidence and this conclusion?”

You are looking for the hidden bridge.

Example:

An assumption could be:

No other major factor caused the increase.

The argument needs that idea.

But you cannot automatically infer it from the facts given.

That is the key difference.

A quick way to remember it:

Inference = supported by the facts.
Assumption = required by the argument.

For assumption questions, the negation test can help: if making the option false damages the argument, it is probably necessary.

For inference questions, do not use that test. Just ask whether the answer is clearly supported.

My rule is simple:

Inference comes out of the evidence. Assumption sits underneath the conclusion.

Once you separate those two jobs, the answer choices become much easier to judge.