A survey was recently conducted among ferry passengers on the North Sea. Among the results was this: more of those wh...

Emil-Kunkin on December 25, 2022

Hi, the author tells us that a greater proportion of people who had taken seasickness drugs got seasick than of those who had not taken such drugs. From this she concluded that the drugs do not have their advertised effect.

This is a flawed argument. The author compares these two groups but ignores the fact that people who take the drug in the first place are likely already predisposed to seasickness. This is classic selection bias.

We are then asked to weaken the argument. D does this perfectly, it tells us that those who take the drugs actually did have an improvement from them. This clearly weakens the idea that the drugs did not help.