attack possible causal conclusion

[Minnie]

One of the most effective method to attack possible causal conclusion is "Raising a possible third cause that could have caused both elements."
Could you give me an example?

[James Finch]

Hi Minnie,

Here's an example:

High School Principal: Last year we had 600 seniors graduate. This year, however, we only had 500 seniors graduate. This is due to large budget cuts that forced us to lay off 20% of our teachers.

If this were a Weaken question and we were given an answer choice that told us that a new high school was opened in the same school district this year, or that stated that enrollment declined by 20%, these could serve as alternate causes for the decrease in the number of graduating seniors.

Alternatively, if it were a Strengthen question and the answer choice told us that enrollment had actually increased or that there were more students in the senior class this year than last year, that information would help eliminate a possible alternate cause and thus strengthen the causal relationship stated in the conclusion.

Hope this helps!