Question 21 is a strengthening question. We're asked to strengthen the journalist's argument.

So let's take a look at what the journalist's argument is. People whose diets contain a relatively large amount of iron are

correlation, we're told a correlation, a positive correlation, between having a lot of iron in your diet and

your chances are developing Parkinson's disease. So

positively correlated. So this is pretty cookie cutter. You identified a correlation A and B.

A is correlated to B. What they then do is instead of

concluding A causes B, which is one way it could be cookie cutter, they did something else.

They assumed that A causes B. They made an assumption that

iron in your diet is what causes you to have a greater chance of developing

Parkinson's. I'm writing this in a different color to show that this is not actually stated in the argument. Rather, it's just assumed or

really, it's like it's derived from this premise. They drew this as a

sub-conclusion from this premise. And once they drew this as a sub-conclusion, they then further draw the actual

conclusion, which is limiting one's intake of meat, seafood, other foods rich in iron, thus reduce one's chance. Which is right.

I mean, if this assumption holds, if eating a lot of iron is

really what increases your chance of developing Parkinson's, sure, then if you cut out iron,

decrease your iron intake, that would lead to a decrease in chance of developing

Parkinson's. Now, the problem with the major

weakness, the problem with this argument, is precisely moving to this causal conclusion,

assuming this causal conclusion, or inferring this causal relationship from this correlative premise, this

correlative observation.

Why is that a problem? Because, as we learn in our core curriculum lessons on causation, when you observe A is correlated with B, A

causes B. I forgot to write cause here, but I guess you this arrow, right, you know, is cause. A causes B

is just one of four possible explanations. What's another like potential possible

explanation for this correlation? You observe this phenomenon. This is one possible explanation.

Hey, here's another. Could it not be that people who are genetically

predisposed to

Parkinson's, right, clearly if you're genetically predisposed to Parkinson's, that's gonna, you're gonna have a higher chance of developing Parkinson's.

But what if people who are genetically predisposed to Parkinson's also happen to just eat more

seafood, meat, and whatever other foods that's rich in iron for whatever reason, because they crave it or something.

Right now, if this were true, you see, you have a totally different explanation of this correlation.

Why do we observe a correlation between people who develop Parkinson's and people who have a high, a high iron in their diet?

It's because they're pre-genetically predisposed. So if that's the case, telling people to cut out their iron,

that's not gonna do anything for their Parkinson's, right? You need to make sure, for this argument to work,

you need to make sure that this is the correct

explaining this phenomenon, then your argument's screwed, right?

That's exactly what A helps you do. A says most people who have a genetic predisposition to Parkinson's disease,

so clearly they are gonna, they are predisposed to develop it, they have no more iron in their diets than people without, right?

So they're explicitly saying, yeah, that's not the case. Well, if this is not the case, it makes it more likely

this is the case. So good. Our argument has helped along, right? That's what makes A right.

The rest of them are pretty terrible, actually. Like B is talking about such a small, narrow slice of people, right?

That's such a narrow slice of people, right? And children and adolescents require more, okay, that's nice.

The iron in some foods is much less, of course, this is true.

You don't expect iron to be like all equally easily absorbable, right?

So what is that supposed to do? And this is like, this is so random at the age of 50.

I did like a double take. I'm like, what? Did I miss something here? Right? No, I didn't. It's just that random.