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I Does this scatter chart really show a cause and effect?

  1. Apr 17, 2017 #1
    I tried to show a link between chicken consumption and obesity. What I came up with is on a web page. You can see it here:
    http://www.maverickexperiments.com/chicken/chickenFat.html

    My question is does the scatter chart at the end of this page valid?
     
  2. jcsd
  3. Apr 17, 2017 #2

    berkeman

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    Looks pretty random to me, as I would expect. You are not accounting for other variables in this -- you would need to somehow remove variations from other factors in order to implicate chicken consumption on its own, IMO.
     
  4. Apr 17, 2017 #3
    This only shows correlation - not cause and effect. For example - consider being obese and this causes the person to crave chicken.

    Or if you looked at body builders - who in general eat a lot of skinless chicken breast, you would be saying chicken breast makes you buff.
     
  5. Apr 17, 2017 #4

    mfb

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    Industrialized countries tend to have more obese people, and they tend to have a higher meat consumption. This is not chicken-specific. You probably get a better correlation if you plot total meat consumption.

    But, as commented already, correlation and causation are different things. You get an even higher correlation if you plot CO2 emissions per person versus the fraction of obese men.

    You can also get great correlations with things that are clearly without causal relation. This website has many of them.
    The number of people who drown in a pool correlates with the number of films Nicolas Cage appears in. What causes what? ;)
     
  6. Apr 17, 2017 #5

    berkeman

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    LOL :biggrin:
     
  7. Apr 17, 2017 #6

    Mark44

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    A couple of points in the scatter chart are interesting. The U.S. and Australia consume almost the same amount of chicken, per capita, but the U.S. percentage of obese people is almost 12 percentage points higher. Also, Poland and Myanmar (Burma, really) consume nearly identical amounts, yet Poland's share of obese people is 28.6% while Myanmar's share is only 3.7%. Clearly, there is something else going on besides the amount of chicken being eaten.
     
  8. Apr 17, 2017 #7

    OmCheeto

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    Yes, something is going on here. But what it is, I'm not sure.
    Anyways, in an attempt to comprehend what my t-shirt means, by this coming weekend, I decided to do a little data mining, and plotting.......

    Code (Text):
    variable____    R^2__     equation_(ax + b)
    calories____    0.7178    0.022x - 46
    rice________    0.6340    -0.15x + 29
    all meats___    0.5959    0.25 + 6.1
    emp-Agricult    0.5415    -0.54 + 30
    cows________    0.4778    0.22x + 13
    emp-Service_    0.4567    0.50x - 9.3
    chickens____    0.4517    0.63x + 6.2
    income______    0.2934    0.0005x + 11
    ave temp____    0.2004    -0.53x + 29
    fish________    0.0744    -0.21x + 26
    leisure time    0.0504    -2.5x + 64
    emp-Industry    0.0267    0.29x + 16
    working time    0.0097    0.0041x + 21
    vegetables__    0.0031    0.0077x + 21
    My conclusions were:
    1. Given that I have never studied statistics, these numbers are kind of gibberish, but somewhat entertaining.
    2. A higher R2 seems to indicate that the data is less random.
    3. No matter how many vegetables you eat, it isn't going to make you skinny, if the other 13 variables are not in your favor.
    4. I will never understand my t-shirt*. :oldcry:

    ------------------------------------
    *Om's "Radical Bayesian" t-shirt:
    The OP's hypothesis was that eating chickens makes you fat.
    My current hypothesis is that nations with low rates of agricultural employment, and high rates of service employment will make you fat.
    How on Earth do you put that into an equation? Do I just plug in the R squares?

    ps. Sorry for the thread hi-jack, but I'm serious. :oldgrumpy:
     
  9. Apr 19, 2017 #8
    There is no question that many other things are going on. My question is. Is there sufficient evidence to show that the chemicals and antibiotics used in the production of chicken may be partly responsible for obesity? Should this possible cause be suspected and studied.
     
  10. Apr 20, 2017 #9

    mfb

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    The plot does not help answering that question at all.
    Even if you could establish a clear link between chicken consumption and obesity (you cannot with the given data), it would not imply that antibiotics and "chemicals" (whatever that means - water is a chemical substance as well) are responsible, instead of the chicken itself.
     
  11. Apr 20, 2017 #10

    What causes that you ask. Simple. The number of films Nicolas Cage appears in is cherry picked from thousands and perhaps millions of sets of data. It is chosen as it happens to match the data for the number of people who drown in a pool.

    To me the statement "correlation does not imply causation" is akin to Newton "finding a beach pebble brighter than most" and then throwing it away. Newtons genius lies not in finding the pebble but in seeing in it what could be derived from it.
     
  12. Apr 20, 2017 #11

    mfb

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    That is the point.
    Why do you think chicken is not cherry-picked from all the foods you could look at? Especially as you would expect a correlation between most foods and obesity, simply due to regional differences.
     
  13. Apr 20, 2017 #12
  14. Apr 20, 2017 #13

    OmCheeto

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    Chickens.......
    hmmm....
    Two years ago, I built a garden, and had more tomatoes than I knew what to do with.
    Last year, I got one tomato.

    My growth rate went down by about a factor of 100.

    But previous to that, I tried to grow tomatoes in my "alt-garden".
    The growth rate there was consistent with my last years growth rate in my "neo-garden".

    Conclusion?

    Water and feed(solar and nutrient-wise) your tomatoes, and you will get lots.

    As to your chicken double growth rate assertion?

    Ummm.......

    Do you have any sources for that?
     
  15. Apr 20, 2017 #14
    • • Sure here:
    • Conventionally bred broiler chickens: Most of the chicken available in the stores today comes from flocks that grow to market weight in about 48 days on average, using fewer natural resources – therefore more sustainably. Compared to 25 years ago, today’s chickens now require seven percent less feed per pound to grow. Considering our national broiler flock eats about 57 million tons of feed per year that is a lot of resources saved.

    • Slow growth/Heritage broiler chickens: “Slower-growing” chickens or “Heritage breeds” are chickens that can take almost twice as long to reach market weight – about 81 days typically – because they do not convert feed to muscle as quickly. Because of this, these breeds require more feed, fuel, water and land per pound of meat to sustain their growth. As such, these products are typically 3x more expensive than their counterparts.

    from

    http://www.chickencheck.in/faq/difference-faster-slower-growing-chicken/

    Al
     
  16. Apr 20, 2017 #15

    mfb

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    We managed to more than double the yield of basically every crop. So what?
    Even 100% correlation would not make a case at all.

    Unrelated: Calculate the correlation instead of putting your plot next to a random 50% correlation plot.
     
  17. Apr 20, 2017 #16

    Merlin3189

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    Interesting difference in perspective. To me it looked a pretty good correlation, well worth doing the stats* (which would have been without the aid of a mechanical calculator.) But that was the perspective of a psychology student, rather than a P/S/M/E graduate.

    * to evaluate the correlation, NOT to show any causal link.
     
  18. Apr 22, 2017 #17
    You are mixing up growth rate and yeld.
     
  19. Apr 22, 2017 #18
    Thanks for the response. It appears to me there is some correlation and that a further look is justified. Thats all.
     
  20. Apr 22, 2017 #19

    mfb

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    I am aware of the difference. So what? You propose a causal effect that is not backed by any experimental data or any plausible biological mechanism shown so far. Why do you expect an effect with chicken and not an effect from massive increases in crop yield?
     
  21. Apr 22, 2017 #20
    You ask an important question, and your hypothesis may be correct.

    However, as others have pointed out, you haven't quite proved that eating food with more growth hormones causes more obesity. You are not plotting obesity vs the consumption of growth hormones, only vs. the consumption of chicken. So we don't really know how much, if any, growth hormones contributes to obesity, just based on your presentation. For one thing, the amount of growth hormones present in chicken may vary from country to country.

    Perhaps you could get data that would allow you to make two graphs. One would show obesity vs. consumption of organically grown chicken, and the other vs. consumption of chicken who are raised using growth hormones.

    I think weight gain or loss in general is well understood. There is actually an equation that predicts weight loss based on your age, gender, current weight, amount of physical activity, and projected calorie intake. The version of this equation I used does not distinguish between calories from fats, carbohydrates, or protein. It also does not distinguish between foods with or without growth hormones.

    I went on a very simple calorie restricted diet where I ate whatever I felt like eating, but limited my daily calories. I actually drew a straight line when I began the diet, based on the equation. I compared my daily weight with the prediction line. The experimental result matched the theoretical result very well indeed. Sorry, I don't have the link to the equation, but it should be easy to find.

    In any case, I like your question because I am one of those who prefers organic food and stays away from the growth hormones as much as possible.

    I think statistics is not an easy subject. I found it all a bit confusing until I read Perry Hinton, Statistics Explained.
     
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