| 21. | In contrast, an observational study does not involve experimental manipulation.
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| 22. | For the majority of questions, we have no choice but to use observational studies,
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| 23. | Well-publicised observational studies find that first borns have slightly higher IQ than later borns.
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| 24. | Several very large observational studies have also found elevated risk of heart attack from rofecoxib.
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| 25. | We need to look at all the available data and not discount the observational studies.
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| 26. | That's what you can't tell from observational studies ."
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| 27. | Observational studies show a strong association between delayed intestinal transit and the production of methane.
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| 28. | However, observational studies have raised concerns about negative effects of weight loss and weight cycling.
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| 29. | This is done through repeatable experiments or observational studies.
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| 30. | The negative effects are found in several observational studies.
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