This argument is Q26 in the Critical Reasoning Practice Questions in the 13th Ed. of the GMAT Official Guide.  Let’s work through it in the steps I discuss in this post.

1.  The stem reads: “Which of the following conclusions can most properly be drawn from the information above?” This may sound like it doesn’t fit neatly into my DESTROY, SUPPORT, DESCRIBE framework, but it actually does.  When you are asked to draw a conclusion from an argument, you may not make any assumptions.  This means that the correct answer is an amalgamation of what is in the argument already, and therefore is a DESCRIBE question.

2.  The argument reads:

When a polygraph test is judged inconclusive, this is no reflection on the examinee.  Rather, such a judgment means that the test has failed to show whether the examinee was truthful or untruthful.  Nevertheless, employers will sometimes refuse to hire a job applicant because of an inconclusive polygraph test result.

This is actually all premise (you get to come to a conclusion), though the facts have some discrepancies.

3.  I do not worry about how I happen to know that polygraph testing in general is highly unreliable with lots of false positives.  This is not relevant.

4.  Okay, I don’t need to look for assumptions, I just need to describe.  But it is still useful to simplify the argument to build my description:

(1) Inconclusive = meaningless re applicant.  (2) Inconclusive = bad test.  (3) Inconclusive –> employers turn down applicants.

Which answer choice combines these 3 statements accurately?  Let’s do this by process of elimination.

• (A) Most examinees with inconclusive polygraph tests are in fact untruthful.  This says that Inconclusive = usually untruthful re applicant.  Contradicts (1).
• (B) Polygraph tests should not be used by employers in the consideration of job applicants.  This says that Inconclusive + Conclusive results = useless.  We know nothing about Conclusive results.
• (C) An inconclusive polygraph test result is sometimes unfairly held against the examinee.  We know that Inconclusive = meaningless re applicant (1), and Inconclusive –> bad outcome for applicant.  Since suffering a bad outcome for something that you did not control can be described as unfair, this answer choice is not totally sucky.
• (D) A polygraph test indicating that an examinee is untruthful can sometimes be mistaken.  The argument tells us nothing about conclusive results. Note Step 3!!!
• (E) Some employers have refused to consider the results of polygraph tests when evaluating job applicant.  The argument only tells us about how employers use polygraph results, nothing about how they don’t use results.

You should be hyper wary of (C) because of its use of a value-laden word “unfairly.”  Almost always, these answer choices are traps.  But here is an exception worth noting, and you can be confident that it is an exception because the other choices are so badly wrong.