William M. Briggs

Statistician to the Stars!

Scientists Hint That Water Perhaps Might Possibly Be Good For Kids

9554713013_aacc899a7e_h

When I was a kid they had these things called drinking fountains in public places. Schools had ’em, too. They stood about yea-high. You’d push a button and water would come out which you could drink. This was before scientists figured out how to sell plastic-encapsulated water at enormously inflated rates. Progress.

There’s been so much progress that it’s hard to find water fountains these days. The scarcity got some scientists thinking: what would happen if water were available to school kids? And not just water. Water jets. Yes, water which has been “electrically cooled [in] large clear jugs with a push lever for fast dispensing”! Which sounds even more expensive than bottled water.

Enter Amy Ellen Schwartz and three others who give us the peer-reviewed study “Effect of a School-Based Water Intervention on Child Body Mass Index and Obesity” in JAMA Pediatrics, in which we learn that, scientifically speaking, “Water is essential for human function”. This is why “Previous studies found providing water to students in schools may be beneficial.” May. Scientists are known for their caution.

What Schwartz et al. did was to look at the age-sex normalized BMIs of about a million New York school kids (the government helpfully tracks this none-of-their-business information). If and on what date each kid’s school got a $1,000 water jet was noted. They also found out how much milk was sold at each school’s cafeteria (chocolate or plain was also noted).

Here comes the science: “We identified a student as being ‘treated’ by a water jet if he or she spent 60 or more cumulative school days in a school with a water jet.”

In plain English, this translates to: “We have no idea how much water any kid drank. But we like to say water jets. Try it. Water jets. It’s fun and expensive! And it’s scientific.”

The science didn’t end there. They also scrutinized “changes in milk purchases between schools that had a water jet and schools that did not have a water jet, before and after introduction of a water jet.”

At this point, Schwartz and pals could have noted the differences in BMIs and milk purchases between water jet and non-water jet kids. But no. Instead, they stuck all the data inside a series of regression models. Because regression models are more scientific than just looking at numbers.

Turns out by “policy design, water jets in New York increased over time during our analysis period, and machines were often placed in schools in waves”. Sounds like somebody’s brother-in-law is in the water jet business, no? Skip it.

The shocking main results. “There was a significant main effect of water jets on zBMI, such that the adoption of water jets was associated with a 0.025 (95% CI, ?0.038 to ?0.011) reduction of zBMI for boys and a 0.022 (95% CI, ?0.035 to ?0.008) reduction for girls (P?<?.01).” Wee p-values!

Did you see that? A whopping 0.025 reduction in age-sex normalized BMI for boys. And a stunning 0.022 cliff dive for girls. Scientifically speaking, these differences fall into the Preposterously Trivial classification, which is one step above What Do I Look Like, An Idiot? level. (The same kind of finding for milk was presented.)

Then again, since these are actually parameter estimates from the series of regression models and not actual reductions, Preposterously Trivial is probably an overstatement. And since nobody has any idea whatsoever how much water any kid drank, even What Do I Look Like, An Idiot? is too high. We’re probably much closer to I Weep For The Future Of Humanity classification.

Let’s see how Schwartz describe their success: “Analyses revealed that zBMI and overweight decreased significantly for boys, and zBMI and overweight also decreased significantly for girls.” Note that, despite appearances, “significantly” has no connection to any English word: it is merely to note the p-values were smaller than the magic number. The authors also note that “some children might not like white milk.”

A “potential mechanism” to explain the dramatic changes was that, possibly, “students consumed fewer [sugar-sweetened beverages] brought from outside school”. But the authors have no idea, because they have zero clue what any kid drank.

What we have here is the epidemiologist fallacy in all its glory, married to misused and misunderstood statistical models. The epidemiologist fallacy is when a scientists says X causes Y but where X was never measured. Here X = water jets, and Y is the stupid small change in BMI, and even that was exaggerated by the statistical model.

Just to show you how harmful this fallacy is, one newspaper said the “study found making water available through self-serve dispensers in school cafeterias results in student weight loss.” Sheesh.

This is an official entrant for 2016’s WMBriggs.com Bad Science of the Year Award.

27 Comments

  1. Dieticians HATE this one weird trick to lower your BMI by 0.025!

    It’s like no one even looks at the parameters any more! If the p-value is small, then slap some causality on a plastic lunch lunch box and now they wanna sell it.

  2. Wonder if they put diuretics in the water. Not measuring restroom visits surely is a flaw in this study.

  3. What’s crazy is with our modern technology and surveillance state, one actually *could* design a study to measure the amount of water consumed at these “water jets” by individual students, and compare it to the amount of water consumed at a school without one of these fancy contraptions. But this would require time, effort, and school (and maybe parental) buy-in. Plus of course you wouldn’t know how much water was being consumed outside of school. And if you find an interesting correlation, then you need to do multiple follow ups where you install one of these in more schools, make a prediction about the effects, and measure them. An awful lot of time (years!) before you find a result. In the mean time your competitors for the grant money have released 15 studies about how little Sally Muckenfutch is healthier and/or unhealthier than ever because of the replacement of water with Brawndo sports drink (it’s got electrolytes!)

  4. Briggs, you must be getting senile.

    You left out the single most important finding in the paper!

    To wit: “Further study is needed.”

  5. Maybe bottled water is progress if you live in Flint, MI. Bottled water would have been a great idea there.

    “Preposterously Trivial classification, which is one step above What Do I Look Like, An Idiot? level” Well said! I personally go with the “I Weep For The Future Of Humanity” classification.

    It’s going to be tough to beat this for bad science, but the year is early and I have hopes!

  6. There must be a statistical correlation between the number of PhDs and the opportunity for discovery. There are indeed so many with so little to do, they are changing the names of their disciplines from say meteorologist to climate scientist to garner attention.

    Water was an interesting topic given Flint’s crisis. That science was simple. Change source water PH and dissolve accretions in the distribution system. So simple that even an engineer could have predicted it with high confidence.

    This points to an interesting phenomena. There are so many yearning for scientific fame and fortune that the value proposition of the “discovery” is lost. Who cares about the “Effect of a School-Based Water Intervention on Child Body Mass Index and Obesity.” How could the topic be important given a child only spends 25-percent of a day in school, if indeed, attending at all.

    Needless complexity aimed at irrelevant topics. Sounds like a climate change model…

  7. Yep, needless complexity. I’d call it knitting with numbers.
    The study didn’t need doing.
    Some problems don’t need “science.”

    “Water is essential for human function”. Profound, it’s shaken me to the core.
    I’m going to have tea.

  8. FROM THE STUDY’s SUMMARY: “Water jets were associated with a 0.9 percentage point reduction …in the likelihood of being overweight for boys and a 0.6 percentage reduction … in the likelihood of being overweight for girls …. We also found a 12.3 decrease …in the number of all types of milk half-pints purchased per student per year ….

    IN OTHER WORDS – having water made readily accessible, apparently, induced the kids to quench their thirst with easy water to some small extent offsetting milk consumption, and, presumably, soft drinks.
    That’s kind of obvious…so is the observed result of 0.9 or 0.6 % weight reduction for boy/girl statistically significant, or how significant, relative to the variability in the measure of an overall average weight?

    And, perhaps more important, the reduced consumption of milk is undoubtedly bad as this deprives the children of important nutrition…with the Association of Dairy Farmers will undoubtedly raise as an offsetting negative outcome…

  9. By the way, what’s the difference between a water jet and a drinking fountain?

  10. According to Medscape, “Water jets are electrically cooled, large, clear jugs that oxygenate, chill, and dispense water quickly. They cost about $1000 per machine.”

    There’s a picture here: http://medicalresearch.com/wp-content/uploads/water-jet-1.jpg

    They look like the water machines you find in offices. I would note that these are probably more sanitary than drinking fountains. (I won’t relate what things I have heard of people doing in water fountains—some of you may be eating….) Or maybe that was just one of those “mom myths” from my childhood? Not sure.

  11. As kids, we were told to let the fountain run for a few seconds before drinking. Also, I knew a man once who made it point to drink from every fountain he passed. This was about 20 years ago, and there were more drinking fountains in public places.

    The water jets will definitely eventually harbor something unsavory, esp. if boys are attracted to it. (Oh dear, is that sexist?)

  12. Water might be good for kids but W.C Fields didn’t think it was necessary for himself saying , “I don’t drink water,” and citing something about fish and reproduction.

  13. Sander van der Wal

    January 25, 2016 at 1:52 pm

    The Singularity is indeed upon us. Because people are getting more stupid all the time, and they won’t have a clue about the most trivial of programs, like “Hello, World”.

  14. We had water fountains at the high school I attended many years ago but I rarely used them since the water was foul tasting, not like the sweet well water at home at the other end of the village. I never did figure out to what the difference in taste was due. I walked home for lunch and thus was not obliged to drink the Stygian water that the bused in students were left with.

    The water fountain was often turned into a jet with the proper finger placement in order to spray passers by. This was a very popular pastime which had the added benefit of demonstrating one of Bernoulli’s laws.

    I have never understood the bias against bottled water which I would place as one of the great inventions of modern civilization. It is all part and parcel of the general improvement in sanitation and the disappearance of public water fountains must surely have decreased the spread of communicable decease. People who are upset with bottled water do not blink an eye as concerns other bottled beverages. Strange, is it not?

    The claim of a reduction in obesity (BMI) is too funny for words. Active kids will pick up needed calories wherever they are available or will become less active. You can’t fool Mother Nature. Maybe the next advance in school cafeteria menu is the bread and water diet. Where cigarettes are the medium of exchange in prisons, it will be chocolate bars at school.

  15. The abstract says, “This quasi-experimental study…” What is a “quasi-experimental study”?

  16. “We also found a 12.3 decrease (95% CI, ?19.371 to ?5.204) in the number of all types of milk half-pints purchased per student per year (P?<?.01)."

    Boy, that's gonna cut into the school system's already-stretched budget.

  17. SteveBrooklineMA

    January 25, 2016 at 3:56 pm

    Indeed, today there is no fountain at the corner shown in Briggs’ pic.

    https://goo.gl/maps/rGLKPdj16Fk

    It seems to me people are more concerned about hydration today though. They can’t go anywhere without a water bottle.

  18. Alan Watt, Climate Denialist Level 7

    January 25, 2016 at 4:14 pm

    Did they even consider the possibility that global warming is responsible for reducing the BMI of these kids? During the time of the study surely we must have had 0.0001 +/- 0.05 °C of warming. And isn’t that supposed to lead to smaller people?

    Or wait a minute; maybe we’re supposed to produce smaller people to help combat climate change.

    My bad.

  19. Plan parenthood video author indicted and plan parenthood cleared by a Texas grand jury of any wrongdoing.

    This means that all of you are liars.

  20. Phil R – Quasi-experimental studies differ from experimental ones in that they are not controlled and their sample doesn’t match the population. But, they’re more feasible to do and avoid certain ethical dilemmas, so they are common in nursing and healthcare research, like public health.

    In quasi-experimental designs, subjects are not randomly assigned to groups, so cause and effect conclusions are weaker than in experimental designs, and generalization is limited. These designs use convenience groups, like captive children, er, uh, students…The groups will likely have different characteristics so extraneous variables are introduced, which are analyzed statistically, making everything hunky-dory…

  21. http://www.chron.com/news/houston-texas/article/Harris-grand-jury-indicts-pair-behind-Planned-6782865.php

    So funny the morons behind the fake video are facing 20 years of prison following an investigation ordered by a republican governor.

    And the guy has a second indictment for trying to by tissue illegally. The moron even created a company.

    You guys are so gullible. No wonder you always lose in court.

  22. What water fountains mean are less money in the pockets of the friends of the school board. Other than juice or milk, it should be the only thing, too.

    JMJ

  23. SteveBrooklineMA , great detective work!

    How did you discover the pic’s locale?

  24. Sheri, thanks for the link.

  25. @SteveBrooklineMA Nice link.

    Note if you rotate the view 180 degrees, there are now *public toilets* nearby. But no water fountain. Maybe the fountain was moved to just outside each toilet? It always seems in office buildings in the USA there is a water fountain just outside most toilets.

  26. SteveBrooklineMA

    January 26, 2016 at 9:44 am

    Bob- I used google image search to get more info on the pic. One link gave the general location. I poked around with google maps until I found the spot. I do this sort of thing once in a while… kind of fun, and satisfying when you find it.

    Nate- I like the way you think! Indeed, I poked around the whole park the best I could using street view, but didn’t see a fountain. It could be there though, it seems the toilets are underground.

  27. The paper illustrates one of the reasons why academic statisiticans don’t value many medical-related publications.

Leave a Reply

Your email address will not be published.

*

© 2016 William M. Briggs

Theme by Anders NorenUp ↑