Of the 60 participants in a clinical trial, 30 participants were

Question

Of the 60 participants in a clinical trial, 30 participants were considered to be in the experimental group, and were administered a large dose of an experimental painkiller called nexaphedrinol, while the 30 remaining participants were considered to be in the control group, and were administered the same dose of a placebo. Afterward, participants in the experimental group exhibited fine motor skills that were more diminished than those of the control group. The observed detrimental effects on fine motor skills were attributed to a compound in nexaphedrinol called phedrine, which temporarily damages nerve endings.

Which of the following, if true, would best support the conclusion that a certain compound in the painkiller was responsible for the observed results?

A. Nexaphedrinol has been found to be the most effective painkiller available in a variety of preceding experiments that utilized similar methodologies.

B. Phedrine is a relatively ubiquitous compound found in a variety of medicines, some of which may have been taken by the participants in the experiment.

C. The placebo administered to the participants in the experiment did not contain phedrine but may have contained a compound with similar effects on nerve endings.

D. All the participants in the experiment were found to have had comparable fine motor skills prior to the administration of the nexaphedrinol or the placebo.

E. Most customers suffering from chronic pain have indicated that they would be willing to suffer a decrease in fine motor skills in exchange for an effective painkiller.

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cdrectenwald · Answer

To support the conclusion that phedrine in nexaphedrinol caused the diminished fine motor skills, we need evidence that the experimental group and control group were similar in their fine motor abilities before the trial began. If they started with comparable skills, then any difference observed afterward is more likely due to the treatment—specifically, the phedrine compound in nexaphedrinol.

This makes choice (D) the strongest support for attributing the observed effects to phedrine.

This makes choice (D) the strongest support for attributing the observed effects to phedrine.

Abdelaali91 · Answer

One way in which we can support a cause and effect claim is to discard any outside factors.
Answer choice D is the best contender that denies the outside agent that could be respnsible for the observed events : participant didn't have the same fine motor skills before the experiment.

ROMLIN · Answer

The correct answer is **D. All the participants in the experiment were found to have had comparable fine motor skills prior to the administration of the nexaphedrinol or the placebo.**

**Explanation:**
The conclusion that the compound "phedrine" in the painkiller caused the diminished fine motor skills relies on the assumption that the differences in motor skills observed after the experiment are due to the administration of nexaphedrinol (and its compound phedrine). For this conclusion to be supported, it must be established that any difference in fine motor skills between the experimental group and the control group was due to the treatment and not because the groups were different to begin with.

Answer **D** strengthens the conclusion because it ensures that the participants in both groups started with comparable fine motor skills, meaning any changes observed can more confidently be attributed to the treatment (nexaphedrinol) and not to pre-existing differences. This makes it the strongest support for the conclusion.

Other options do not directly support or strengthen the specific claim about phedrine's effects:
- **A** talks about the effectiveness of nexaphedrinol as a painkiller, but does not address the issue of fine motor skills.
- **B** introduces the possibility that participants might have already taken other medicines containing phedrine, which could weaken the conclusion rather than support it.
- **C** suggests that the placebo might contain a similar compound, which again introduces doubt rather than supporting the conclusion.
- **E** is irrelevant to the conclusion, as it focuses on customer preferences rather than the cause of the diminished fine motor skills.

Bunuel · Answer

Knewton Official Explanation

We're told that in a clinical trial 30 people in an experimental group were given a painkiller and 30 people in a control group were given a placebo. The people in the experimental group had poorer fine motor skills when the experiment was over than the people in the control group.

The author concludes that something in the painkiller causes the lack of fine motor skills. The question asks us to support this argument. Therefore, we're looking for an answer choice that proves that the painkiller, not some other factor, is the cause of the poor fine motor skills.

Choice D  tells us that before the experiment began, all participants in the trial had comparable motor skills. This means that after the experiment, none of the participants had bad motor skills simply due to a preexisting lack of coordination or a muscular disorder. It must have been the drug that they took--the only thing that happened between the beginning and the end of the experiment.  Choice D  strengthens the argument and is therefore correct.

Choice A  states that nexaphedrinol has been found to be an effective painkiller. In fact, this is not at all the issue in this argument. The argument states that the painkiller has a detrimental effect on fine motor skills; the effectiveness of the drug is not at issue.

Choice B  states that phedrine (the compound that is said to be responsible for the loss of fine motor skills) is found in other medicines, and this choice implies that the control group may have been tainted by it. This is a serious accusation; however, we are looking for a strengthener of the claim that the phedrine in the painkiller caused the loss of fine motor skills. If the experiment were tainted, and people in the control group did not exhibit this symptom to the same extent, that would weaken the argument, not strengthen it.

Choice C  states that the placebo may have contained a compound with an effect similar to phedrine's (temporary damage of nerve endings). This choice weakens the conclusion, by implying that the control group may have been affected in the same way, chemically, as the experimental group, without similar results on nerve endings.

Choice E  implies that customers might be willing to suffer a loss of fine motor skills in order to relieve pain. This is besides the point; the claim that the nexaphedrinol caused the loss of fine motor damage in the first place must still be strengthened. The conclusion of this argument has nothing to do with the willingness of customers to take the painkiller.

Answer: D

Of the 60 participants in a clinical trial, 30 participants were

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Of the 60 participants in a clinical trial, 30 participants were

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