Hey John —
Glad to hear that you’ve found the Trainer useful thus far and thanks so much for the comments — it’s awfully nice of you to say and I appreciate it —
In terms of the your first question (about I) — that is a typo, and you are absolutely correct to say that an answer that is sufficient should of course strengthen.
I’m so terribly sorry about that — I honestly can’t remember the last time someone has found an error of significance like that, and I can’t believe it’s lasted until now without any other student noticing and mentioning it — I used to, when the book first came out, offer a $10 Amazon gift card reward if anyone found an error — if you don’t mind, I’d love to send you one now for your troubles — just message me the email address you want it sent to — sorry again, and thanks for letting me know — I’ll fix it immediately.
In terms of Set B — the issue is a very subtle and sneaky one — notice that the conclusion itself is about correlation, not causation.
The author is not making a claim about sleeping concerns causing anxiety and depression as opposed to anxiety and depression causing sleeping issues, etc., but rather about whether there is a correlation between amount of sleep and anxiety and depression in the first place —
Neither H nor I have a direct impact on that correlative conclusion.
To illustrate with an analogous situation, imagine the following argument (please forgive any small wording issues):
“Research has shown that adults in the top 1% in terms of total wealth and adults in the lowest 1% in terms of total wealth work, on average, about the same number of hours per week. This shows that there is minimal correlation between the amount that one works and the amount of wealth one builds up.”
So what’s wrong with this argument? Those extremes aren’t enough to show that there isn’t actually any correlation —
Maybe the super-rich don’t need to work and the super-poor can’t work, but that’s beside the point — the important thing is that —
Maybe for the other 98% of people in between those two extremes, there is a very strong correlation between the amount of hours worked and the amount of wealth accumulated.
Now, notice that in this analogy, whether having more wealth causes those in the 98% to work more (or less), or working more causes one to have more wealth (or less), doesn’t impact the argument reasoning one way or the other —
Either way, the argument hinges on whether the correlation exists or it doesn’t, and that’s the same situation we have in Set B.
Hope that helps clear things up and let me know if you have any follow-up q’s —