What is the passage's central argument?

Because many forces make patients seem better, only a controlled comparison can credit a treatment. (The passage names the forces that mimic a cure, then presents the controlled trial as the way to separate the drug's effect from everything else.)

In the controlled trial described, who does not know which treatment a patient received?

Neither the patients nor the staff judging them. (The third paragraph says neither the patients nor the staff judging them know which is which.)

A clinic reports that seventy percent of its patients improved after starting a new therapy. How would this passage read that figure?

As nearly uninformative, because most patients improve anyway and no comparison group is given. (The passage says almost everyone improves after treatment, so a figure without a comparison group cannot show that the therapy caused the change.)

In this passage, 'inert' means:

having no active effect of its own (The inert tablet is the fake treatment; it is contrasted with a real painkiller, so inert means it does nothing on its own.)

The Sugar Pill Problem: Level 5 Reading Comprehension Questions

Give a patient an inert tablet, tell them it is a strong painkiller, and a fair number will report less pain. The result is real and repeatable, and it is why medicine cannot judge a treatment by asking whether patients improved. Almost everyone improves after treatment. The question is whether they improved because of it.

Several forces push the same way at once. Illness is not steady; people seek help when symptoms peak, and symptoms that peak tend to fall again on their own. Expectation shapes what is felt, and the ritual around a treatment, the examination, the confident voice, the price, has effects of its own. Reporting is not neutral either: a patient who has been given something, and a doctor who gave it, both have quiet reasons to notice improvement.

The controlled trial exists to strip these out. Two groups, assigned at random, receive the real treatment or a convincing imitation, and neither the patients nor the staff judging them know which is which. Whatever the two groups share is subtracted; only the difference is credited to the drug.

The design is powerful, and it is not perfect. Placebo effects act mainly on what a patient reports, such as pain, sickness, and mood, and much less on what an instrument measures.

Comprehension questions