PrepTest 154

Incorrect. If this was true, the doctor probably wouldn't have needed to experiment with a cortisone shot to figure out if the pain was caused by an inflamed nerve. The scan itself would have given them enough information! When negated, this doesn't hurt the argument, so it's not a necessary assumption.

Incorrect. When negated, this tells us that the cortisone shot did reduce pressure on the inflamed nerve. This would strengthen the argument. We're looking for something that, when negated, destroys the argument.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Strengthen with Necessary Premise

Stimulus Summary:
The doctor had a patient experiencing back and leg pain. Scans showed that there was pressure on a particular nerve, which might cause nerve inflammation. The patient got a cortisone shot, which would reduce nerve inflammation if it was present. Since the patient was much relieved by that treatment, it must be true that the nerve caused their pain to begin with.

Answer Anticipation:
Remember, causal conclusions are the easiest kind to attack, so this argument is pretty weak. In order to see it as potentially valid you'd need to make assumptions that all of the numerous alternative explanations (besides nerve inflammation effectively treated with cortisone) for the pain relief are false. For instance, we'd have to assume that cortisone shots don't always produce relief of back and leg pain regardless of the cause. If they always lead to pain relief, they aren't useful for diagnosis. So, we're probably going to find a correct answer choice that, when negated, says the cortisone would have relieved the patient's pain even if they didn't have an inflamed nerve.

Answer Explanation:
The good ol' placebo effect comes out to play! When negated, this gives us the proposition that the pain relief was a total placebo, making it useless as a tool for diagnosis. That would destroy the doctor's claim that the results of their cortisone injection support their diagnosis, making this the correct answer.

Key Takeaway:
Be strict with yourself about negating each answer choice before selecting or eliminating it on Strengthen with Necessary Premise questions (assuming of course that the answer choice strengthens the argument). Only negation can tell you absolutely whether or not a particular assumption is necessary to the argument. If you don't negate, you'll leave points on the table.

Incorrect. If there were some treatment other than cortisone to relieve the inflammation of such nerves, that wouldn't mean cortisone doesn't achieve the same thing. Just because you could take another brand of decongestant and get the same results doesn't negate the fact that if one decongestant improves your headache, you were probably congested.

Incorrect. This could be untrue and yet, it could still be true that the doctor correctly diagnosed the patient. Maybe most back and leg pain has nothing to do with inflamed nerves, but for back and leg pain that is caused by nerve inflammation, cortisone is the right treatment.