7 ms·

"Four men and four women participated in two trials" I'm not a medical researcher; is this a normal size for a study?

sbr464 6y ago
I thought the exact same. I honestly think this post should be deleted on that fact.
bcoates 6y ago
It's enough for such a large effect, but obviously it doesn't tell us anything about the long-term impact of trying it as a lifestyle.
- tgv 6y ago
  There are two problems: "No differences (p>0.05) between interventions were found for plasma insulin or glucose AUC." That can very, very much be explained by lack of power. But the main problem is that a group of 8 people has a very low probability of generalizing across the population. And of course, very few people sit 8 hours without moving. That said, it's more than promising enough for further research.
monkeypizza 6y ago
Say you are trying to distinguish between a placebo and a cyanide pill; test subjects are young rats (base rate of death extremely low). How large of a sample size do you need? I think one control, one test subject is enough to be certain, because the base rate of death is insanely low, when measured on a per-minute basis. Sample sizes can be small and still very significant when the effect is large.
- gvjddbnvdrbv 6y ago
  I would want about four of each rat still. The control could die of something else...
  - samatman 6y ago
    I'm quite confident the only reason to use four rats in a study of cyanide is that you really want to kill two rats.
    - steerablesafe 6y ago
      Yeah, because you already have a very well-established prior on the effects of cyanide.
- buran77 6y ago
  > when the effect is large You mean when the effect is guaranteed. Cyanide is reasonably guaranteed to have the expected effect every time which is why you don't even need the control. With only 4 test subjects you can't really draw a strong conclusion.
a3n 6y ago
Maybe it's a relatively quick and cheap way to decide if it's worth doing larger and longer studies.
- alexilliamson 6y ago
  Voice of reason
mywittyname 6y ago
Medical research is expensive to conduct, so it's not uncommon to see N<20. Additionally, more data is not necessarily better data since humans lie and it's unethical to force their compliance, so there's more of a risk for bad data with large trials. And throwing out bad data is selection bias.

I thought the exact same. I honestly think this post should be deleted on that fact.

It's enough for such a large effect, but obviously it doesn't tell us anything about the long-term impact of trying it as a lifestyle.

tgv 6y ago
There are two problems: "No differences (p>0.05) between interventions were found for plasma insulin or glucose AUC." That can very, very much be explained by lack of power. But the main problem is that a group of 8 people has a very low probability of generalizing across the population. And of course, very few people sit 8 hours without moving. That said, it's more than promising enough for further research.

monkeypizza 6y ago

Say you are trying to distinguish between a placebo and a cyanide pill; test subjects are young rats (base rate of death extremely low). How large of a sample size do you need? I think one control, one test subject is enough to be certain, because the base rate of death is insanely low, when measured on a per-minute basis. Sample sizes can be small and still very significant when the effect is large.

gvjddbnvdrbv 6y ago
I would want about four of each rat still. The control could die of something else...
- samatman 6y ago
  I'm quite confident the only reason to use four rats in a study of cyanide is that you really want to kill two rats.
  - steerablesafe 6y ago
    Yeah, because you already have a very well-established prior on the effects of cyanide.
buran77 6y ago
> when the effect is large You mean when the effect is guaranteed. Cyanide is reasonably guaranteed to have the expected effect every time which is why you don't even need the control. With only 4 test subjects you can't really draw a strong conclusion.

a3n 6y ago

Maybe it's a relatively quick and cheap way to decide if it's worth doing larger and longer studies.

alexilliamson 6y ago
Voice of reason

mywittyname 6y ago

Medical research is expensive to conduct, so it's not uncommon to see N<20. Additionally, more data is not necessarily better data since humans lie and it's unethical to force their compliance, so there's more of a risk for bad data with large trials. And throwing out bad data is selection bias.