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Biostat - abhijeetnakave
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05-31-2007, 11:29 AM
Q. One Dr. is planning to determine prevalence of DM2 in a community....so he took all the population as a sample...then he changed his mind and took only those who has BMI >30...Q is...what will happen due to that cut off point ?
a.increase specificity b.inc senitivity c.decrease prevalence d.inc. PPV e.inc NPV
05-31-2007, 11:45 AM
should be dddd...as this is a subset of population with higher prevelence of diabetes....higher prevalence means increased PPV
05-31-2007, 11:49 AM
i wud go with "A"....not D...becos thers no info on prevalence so cant comment about PPV.. increase the cutoff point and U increase the Specificity..and decrease the cut off and u increase Sensitivity...
05-31-2007, 11:52 AM
well...its not a cut off point for diabetes.....it just selects a subpopulation....so u cant comment about cut off..i think...cut off would be blood sugur level
05-31-2007, 11:56 AM
prevalence of a study group doent affect the sensitivity or specificity
its a predictore of PPV adn NPV
05-31-2007, 12:01 PM
dark horse..ur explanation makes sense to me..guess u are right..wats the answer ...abhijeetnakave..?
05-31-2007, 12:05 PM
makes sense to me but only this way, PPV tell u what the likelihood that a Pt w/ Postitve test is really positive , so if you only concentrate on people with a BMI> 30 that more people will be positive for DM,hence increase in PPV
darkhorse does that makes sense or am I completely off??
05-31-2007, 12:07 PM
" prevalence of a study group doent affect the sensitivity or specificity
its a predictore of PPV adn NPV " I agree....!! since time was less...only 20 to 25 sec....and I saw...prevalence Q...only one option with PPV...I went for it....that was the last one so I remember...!! |
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