Types of Study Designs: Observational : One or group of pts and char are observed, recorded and analyzed. .this is Association (assoc does not imply caus) Experiments: this involves an intervention which has an effect that is investigated on a study subject. This is Causation randomized conrol exper: subj is blinded. double blind exper (maybe placebo-cnrld): researchers and subj do not know which grp pts in. Case-Series Study: Describes char. of sm grp of pts. Worst type. Simple descript. of char, no control Case-Control Study: use with rare cases. starts w/ outcome and looks back to see assoc. (retrospective).has cases who have outcome and controls. .shows assoc btw smoking and cancer no causation.+ bc cheap, but hard to find control grp. Cross Sectional Studies: aka surveys .provides snapshot at certain time of freq and char of pop. Cohort Study: aka prospective study. subj selced by common char and looks forward in time=longitudinal. Q: pts recruited using surveillance sys
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