lecture 14 - Intervention Studies Lecture 14 Experimental...

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1 Lecture 14 Intervention Studies (COHORT STUDY VARIANT) Intervention Studies { Experimental study design { Goal: Test the efficacy of a treatment or other intervention in reducing or preventing disease { Key: Investigators control the intervention or “exposure” { Multi-center randomized controlled trials are the most powerful type of epi study design Intervention Studies { Subjects are enrolled on disease status z All are healthy z All have a specific disease { The investigators control the experiment z Determine who gets the intervention z Determine the dose z Determine the time frame { Monitor subjects to see if the intervention helps to prevent or reduce the severity of disease Type of Interventions { Medications z New drugs z New uses for old drugs z New doses z New populations { Surgery { Educational programs { Behavioral changes { Any combination of the above Intervention Studies: Examples { Folic Acid and Neural Tube Defects { Fosamax and Osteoporosis { Arab American Youth: Tobacco Use and Intervention { Interactions of Depressed Mothers with Their Infants { For a list of clinical trials in the United States, see: www.clinicaltrials.gov . Clinical Trials Occur in Phases { Phase I z Establish effects of new drug in humans z Test in small number of healthy people to establish the optimal dose range { Phase II z Determine therapeutic efficacy in diseased group { Phase III z Test against other therapies or placebo { Phase IV z Test for other uses of the therapy
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2 Intervention Studies: Sample Size { Phase I and II studies are generally small, with a handful of people { Phase III and Phase IV studies generally have a large sample size { Sufficient sample size necessary to: z Improve ability (power) to detect a difference z Improve generailzability to the reference population Define Internal vs. External Validity { Internal Validity z Ability to get true results from the study population { External Validity z Ability to generalize the results to the greater population z Is the study population representative of the greater population? Internal vs. External Validity { Large controlled trials usually have a high degree of internal validity because z Randomization and masking minimize the risk of error z A large sample size makes it more likely that an observed association is not due to chance
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lecture 14 - Intervention Studies Lecture 14 Experimental...

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