Indeed that, to a lesser extent, can be a problem for any study of a human network.
Second, by including the entire eligible Danish population, which is covered by a national tumor registry, the study avoids the problem of selection bias (that is, people who do not make it into your study for various reasons, including refusal).
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To get around this potential problem, the University of Pennsylvania study only examined studies without a washout period.
To give you an idea of how widespread the problem is, a new study to be published in the Journal of Finance and Quantitative Analysis finds that option volume in a specific stock begins to surge three days before unannounced analyst upgrades or downgrades of a company.
"Part of this isn't a sport problem, part of it is a societal problem, " said Dan Gould, director of the Institute for the Study of Youth Sports at Michigan State.
By the end of the study, 215 of the study participants had experienced a heart attack or other cardiovascular problem, and 325 had died from any cause.
Another problem may be the size of the study: just twelve patients.
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This problem is the focus of an important new study by Demographia.
The EU study says says the problem of limited capacity is likely to worsen because many busy airports, including London Heathrow and Paris Orly, do not plan to expand.
And that's a problem, considering the results of the Mobile Mindset Study, a recent survey that found three out of five U.S. smartphone users don't go more than hour without checking their gadgets.
He says part of the problem is that too few people now study classical Greek, Latin or Arabic and there are not enough experts to interpret the original texts.
There had been a lot of forums and papers published, she says, but the field had been handicapped by a tendency on the part of drug companies to approach the problem on a study-by-study basis, often not following up with communities after the work is done.
Carter found that his study was indicative of a more widespread problem in the United States.
Instead the study showed the problem came from making copies of the cancer's genetic code.
"That was actually the predominant problem in patients in our study -- 78 percent of them had health insurance, but many of them were bankrupted anyway because there were gaps in their coverage like co-payments and deductibles and uncovered services, " says Woolhandler.
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There is one problem with this interpretation of their results: the letters in the study were sent from Cambridge, Massachusetts.
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The subjects of the study were asked to solve a particular problem-solving task previously used in other psychology studies researching problem solving.
He wants to see an immediate reduction in pesticide use until the effects are better understood, and is pressing for the formation of a European Union environment unit to study the problem.
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This latest study suggests that this may be less of a problem than previously thought.
Both the Credit Suisse study and the study on the economic benefits of equality avoid this problem.
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The study cited overconfidence as the root cause of the problem.
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The problem, according to a recent study and survey by Jennifer Lawless of American University and Richard Fox of Loyola Marymount University, is that so few choose to run.
Fish oil capsules failed to prevent flare-ups of atrial fibrillation, a common heart rhythm problem, in a large study in 2010.
His study, commissioned by the Pharmacia drugs company, suggests the problem of HAIs is a far bigger cause of bed-blocking than delayed discharges.
And even if we were able to settle upon an acceptable definition of consciousness, we really have no idea how to study the problem.
Dr. Sanjay Gupta, CNN chief medical correspondent: This study says metabolic syndrome is a problem in the United States because of the way we eat: lots of red meat, lots of processed meat, and too much fried food.
But just two years later cardiologists warned of a potential problem: Merck's own 8, 000-person study, the same one that showed Vioxx reduced ulcer complications, also found that patients on the drug had more than double the risk of heart problems of those on another painkiller, naproxen (the ingredient in over-the-counter Aleve).
The problem was that a growing proportion of them did not pursue careers in their field of study.
"When people overtly lie about something, they can take something innocuous and make it into a bigger problem, " says John Caughlin, the study's lead researcher and professor of communication at the University of Illinois at Urbana-Champaign.
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The problem with the study, Diet Soft Drink Consumption is Associated with an Increased Risk of Vascular Events in the Northern Manhattan Study ( Gardner et al., Journal of General Internal Medicine) is that the numbers are low enough to leave us uncertain as to whether diet drinks were the cause or simply correlated with other factors that led to these events.
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