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Old 03-25-2012
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Sphygmomanometer Changing Blood Pressure Measurement of recruited study patients!

An investigator wishes to perform a randomized clinical trial to evaluate a new beta blocker as a treatment for hypertension. To be eligible for the study, subjects must have a resting diastolic blood pressure of at least 90 mm Hg. One hundred patients seen at the screening clinic with this level of hypertension are recruited for the study and make appointments with the study nurse. When the nurse obtains their blood pressure two weeks later, only 65 of them have diastolic blood pressures of 90 mm Hg or more.
The most likely explanation for this is
a. Spontaneous resolution
b. Regression toward the mean
c. Baseline drift
d. Measurement error
e. Hawthorne effect
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Old 03-25-2012
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E) Hawthorne effect
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Old 03-25-2012
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dr.Hawthrone is watching you...
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Old 03-25-2012
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The answer is b. Although hypertension
can resolve spontaneously, this is an unlikely explanation for resolution
over a two-week period in 35% of the subjects.A much more likely explanation is regression toward the mean. Because of random fluctuations, any one measurement of blood pressure may be far from a persons normal blood pressure. By referring patients for the study based on a single measurement,those in whom the measurement was high (which proved later not to reflect the actual BP) are much more likely to be referred than those in whom the measurement was too low. Thus, in any group selected based
on a characteristic with substantial day-to-day variation, many will have
values closer to the population mean when the measurement is repeated
and the worst patients will impr ove.
Neither baseline drift (which occurs
with measurements on certain machines that require frequent calibration)
nor measurement error is as likely an explanation. The Hawthorne effect
refers to a tendency among study subjects to change simply because they
are being studied. It is much more likely to affect studies of behavior or
attitudes than a study of blood pressure.
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Old 03-26-2012
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Regression towards the mean...the most likely other false ans can be hawthorne effect...but...hypertension...cant be physically controlled bu the patient to show fav rrsults...so i m with b
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Old 04-09-2012
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Quote:
Originally Posted by vna.rao22 View Post
...
nor measurement error is as likely an explanation. ...
Tricky to answer such questions. I don't understand why measurement error can't be as likely explanation.

Poorly calibrated apparatus may give rise to error in 35% or even more subjects.
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Old 04-10-2012
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I'd still go with d). people can get nervous around doctors, and their blood pressure often rises as a consequence. they where probably more comfortable and familiar with everything the second time they were measured
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