3 ms·

I don't really see how this hand-wavy dismissal invalidates anything about the study. Both groups of mice were in the same room, and while they would be exposed

I don't really see how this hand-wavy dismissal invalidates anything about the study. Both groups of mice were in the same room, and while they would be exposed to somewhat different levels of noise due to relative distance to the fans, the difference would be negligible. Same for the toxin buildup, the very reason the fans were present was to circulate the air, which was constantly both monitored and regulated. This was a core part of the whole setup and the main focus of the study. Unless you find it more likely that the small background noise difference had a starker effect on the lungs than the mixture of gases going through the lungs constantly, I don't really see how any of the criticisms hold.

radford-neal 5y ago
The fans were to circulate air within the chamber (because they worried, I think incorrectly, that the CO2 might sink to the bottom). There was nothing to stop the smell of urine, and other volatiles, such as outgassing from plastics, from accumulating within the chamber. There's no reason to think the difference in noise was negligible, and noise can have a big effect on things like stress levels, which can have wide-ranging health effects. Plus, there may well have been other effects of the chamber, such as different light levels, which could also have unknown health effects. It's absolutely fundamental for an experiment like this to try to match the exposure and control conditions as closely as possible, aside from the one variable you're looking at. They failed to do this, so their results are worthless.
- 1e-9 5y ago
  > There was nothing to stop the smell of urine, and other volatiles, such as outgassing from plastics, from accumulating within the chamber. The paper states that the substrate and changing schedule had been shown to keep ammonia to low levels. > There's no reason to think the difference in noise was negligible... Actually, there is. A good 80 mm fan can push more than 10 cubic feet per minute at less than 10 dBA. That's far quieter than a human whisper or rustling leaves. It's comparable to the sound of a pin dropping. If mice are adversely affected by that, I don't see how they could survive the wild. > Plus, there may well have been other effects of the chamber, such as different light levels, which could also have unknown health effects. That seems like pure speculation.
  - radford-neal 5y ago
    What about things other than ammonia? And did they have a "good" fan, or a bad fan? The point of making the environment for the exposure and control groups be as near identical as possible is to equalize not only the factors you thought of, but also the factors you didn't think of. It's the idea that there were no important differences between exposure and control groups, despite their obviously different living environments, that is "pure speculation".
    - 1e-9 5y ago
      > What about things other than ammonia? Certainly possible, but it seems more likely that the control group would have been exposed to something harmful from the lab environment air versus the CO2 group that was getting medical air. > And did they have a "good" fan, or a bad fan? The cheapest 80mm fan I can find on newegg.com is a $3.49 Zalman[1] that is 20-23 dBA. That's comparable to the sound of rustling leaves and far less than the sound of a quiet whisper (30 dBA) or a babbling brook (40 dBA). Someone would have to go out of their way to find an 80mm fan that is so bad that it would be louder than a natural environment. > The point of making the environment for the exposure and control groups be as near identical as possible is to equalize not only the factors you thought of, but also the factors you didn't think of. I completely agree. I don't recall seeing a paper I couldn't poke holes in though. The fact that their methods were imperfect does not make the study worthless. They found a modest effect for the given methods. It suggests there may be merit to follow-on studies, which would likely use different methods. That's a useful result that has added new information. [1] https://www.newegg.com/zalman-f1-led-case-fan/p/N82E16835118154 https://www.newegg.com/zalman-f1-led-case-fan/p/N82E16835118...
    - 1e-9 5y ago
      It’s too late to edit my previous comments, but I should mention that I actually agree with your statements about not being able to draw valid conclusions and that they should have used the same kind of chamber; however, I believe the methods were reasonable enough to provide some value.
Ar-Curunir 5y ago
The guy is a Trump supporter. I would not try to reason with him.
- bigfudge 5y ago
  Whilst I might share your frustration, your comment didn't add anything to the debate. The absence of comments like yours (from either side) is one of the reasons I come to HN, and is the reason I downvoted you.
- dang 5y ago
  Please stop taking HN threads further into ideological flamewar, regardless of how wrong someone else is about something or you feel they are. It just makes things worse. We had to warn you about this just a few days ago: https://news.ycombinator.com/item?id=27692859 https://news.ycombinator.com/item?id=27692859. If you wouldn't mind reviewing https://news.ycombinator.com/newsguidelines.html https://news.ycombinator.com/newsguidelines.html and taking the intended spirit of the site more to heart, we'd be grateful.
krastanov 5y ago
The point of control groups is, in effect, to not have to have the conversation we are having. It is incredibly glarring to have such uncontrolled differences between the two groups. I personally tend to believe the results are "correct" and "logical" and "expected", but this belief of mine is how confirmation bias works, hence I can not relly on this experiment exactly because of the reasons OP mentioned.

radford-neal 5y ago

The fans were to circulate air within the chamber (because they worried, I think incorrectly, that the CO2 might sink to the bottom). There was nothing to stop the smell of urine, and other volatiles, such as outgassing from plastics, from accumulating within the chamber. There's no reason to think the difference in noise was negligible, and noise can have a big effect on things like stress levels, which can have wide-ranging health effects. Plus, there may well have been other effects of the chamber, such as different light levels, which could also have unknown health effects. It's absolutely fundamental for an experiment like this to try to match the exposure and control conditions as closely as possible, aside from the one variable you're looking at. They failed to do this, so their results are worthless.

1e-9 5y ago
> There was nothing to stop the smell of urine, and other volatiles, such as outgassing from plastics, from accumulating within the chamber. The paper states that the substrate and changing schedule had been shown to keep ammonia to low levels. > There's no reason to think the difference in noise was negligible... Actually, there is. A good 80 mm fan can push more than 10 cubic feet per minute at less than 10 dBA. That's far quieter than a human whisper or rustling leaves. It's comparable to the sound of a pin dropping. If mice are adversely affected by that, I don't see how they could survive the wild. > Plus, there may well have been other effects of the chamber, such as different light levels, which could also have unknown health effects. That seems like pure speculation.
- radford-neal 5y ago
  What about things other than ammonia? And did they have a "good" fan, or a bad fan? The point of making the environment for the exposure and control groups be as near identical as possible is to equalize not only the factors you thought of, but also the factors you didn't think of. It's the idea that there were no important differences between exposure and control groups, despite their obviously different living environments, that is "pure speculation".
  - 1e-9 5y ago
    > What about things other than ammonia? Certainly possible, but it seems more likely that the control group would have been exposed to something harmful from the lab environment air versus the CO2 group that was getting medical air. > And did they have a "good" fan, or a bad fan? The cheapest 80mm fan I can find on newegg.com is a $3.49 Zalman[1] that is 20-23 dBA. That's comparable to the sound of rustling leaves and far less than the sound of a quiet whisper (30 dBA) or a babbling brook (40 dBA). Someone would have to go out of their way to find an 80mm fan that is so bad that it would be louder than a natural environment. > The point of making the environment for the exposure and control groups be as near identical as possible is to equalize not only the factors you thought of, but also the factors you didn't think of. I completely agree. I don't recall seeing a paper I couldn't poke holes in though. The fact that their methods were imperfect does not make the study worthless. They found a modest effect for the given methods. It suggests there may be merit to follow-on studies, which would likely use different methods. That's a useful result that has added new information. [1] https://www.newegg.com/zalman-f1-led-case-fan/p/N82E16835118154 https://www.newegg.com/zalman-f1-led-case-fan/p/N82E16835118...
  - 1e-9 5y ago
    It’s too late to edit my previous comments, but I should mention that I actually agree with your statements about not being able to draw valid conclusions and that they should have used the same kind of chamber; however, I believe the methods were reasonable enough to provide some value.

Ar-Curunir 5y ago

The guy is a Trump supporter. I would not try to reason with him.

bigfudge 5y ago
Whilst I might share your frustration, your comment didn't add anything to the debate. The absence of comments like yours (from either side) is one of the reasons I come to HN, and is the reason I downvoted you.
dang 5y ago
Please stop taking HN threads further into ideological flamewar, regardless of how wrong someone else is about something or you feel they are. It just makes things worse. We had to warn you about this just a few days ago: https://news.ycombinator.com/item?id=27692859 https://news.ycombinator.com/item?id=27692859. If you wouldn't mind reviewing https://news.ycombinator.com/newsguidelines.html https://news.ycombinator.com/newsguidelines.html and taking the intended spirit of the site more to heart, we'd be grateful.

krastanov 5y ago

The point of control groups is, in effect, to not have to have the conversation we are having. It is incredibly glarring to have such uncontrolled differences between the two groups. I personally tend to believe the results are "correct" and "logical" and "expected", but this belief of mine is how confirmation bias works, hence I can not relly on this experiment exactly because of the reasons OP mentioned.