Quick summary of Doctor, There are Two Kinds of “No Evidence”:
- Author has a relative with cancer. Relative is doing well after chemo and is going to a doctor to see if it's worth getting more chemo to kill the little extra bits of cancer that might be lingering.
- Doctor says that there is no evidence that getting more chemo does any good in these situations.
- Author says that this violates common sense.
- Doctor says that common sense doesn't matter, evidence does.
- Author asks whether "no evidence" means 1) a lot of studies showing that it doesn't do any good, or 2) not enough studies to conclusively say that it does good.
- Doctor didn't understand the difference.
Let me be clear about the mistake the doctor is making: he's focused on conclusive evidence. To him, if the evidence isn't conclusive, it doesn't count.
I think this doctor is stuck in a Valley of Bad Rationality. Here's what I mean:
- The average Joe doesn't know anything about t-tests and p-values, but the average Joe does know to update his beliefs incrementally. Lamar Jackson just had another 4 touchdown game? It's not conclusive, but it starts to point more in the direction of him winning the MVP.
- The average Joe doesn't know anything about formal statistical methods. He updates his beliefs in a hand-wavy, wishy-washy way.
- The doctor went to school to learn about these formal statistical methods. He learned that theorizing is error prone and that we need to base our beliefs on hard data. And he learned that if our p-value isn't less than 0.05, we can't reject the null hypothesis.
- You can argue that so far, the doctors education didn't move him forward. That it instead caused him to take a step backwards. Think about it: he's telling a patient with cancer to not even consider more chemo because there is "no evidence" that it will do "any" good. I think Average Joe could do better than that.
- But if the doctor continued his education and learned more about statistics, he'd learn that his intro class didn't paint a complete picture. He'd learn that you don't always have access to "conclusive" evidence, and that in these situations, sometimes you just have to work with what you have. He'd also learn that he was privileging the null hypothesis in a situation where it'd make sense to do the opposite. The null hypothesis of "more chemo has no effect" probably isn't true.
- Once the doctor receives this further education, it'd push him two steps forward.
- In the intro class, he took one step backwards. At that point he's in the Valley of Bad Rationality: education made him worse than where he started. But then when he received more education, he took two steps forward. It brought him out of this valley and further along than where he started.
I think that a lot of people are stuck in this same valley.