Research Research Curriculum Curriculum Session II –Study Subjects, Session II –Study Subjects, Variables and Outcome Measures Variables and Outcome Measures Jim Quinn MD MS Jim Quinn MD MS Research Director , Division of Emergency Medicine Research Director , Division of Emergency Medicine Stanford University Stanford University
24
Embed
Research Curriculum Session II –Study Subjects, Variables and Outcome Measures Jim Quinn MD MS Research Director, Division of Emergency Medicine Stanford.
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Research CurriculumResearch CurriculumSession II –Study Subjects, Session II –Study Subjects,
Variables and Outcome MeasuresVariables and Outcome Measures
Jim Quinn MD MSJim Quinn MD MS
Research Director , Division of Emergency MedicineResearch Director , Division of Emergency Medicine
Stanford UniversityStanford University
OverviewOverview
Study SubjectsStudy Subjects- SamplingSampling
- RecruitmentRecruitment
VariablesVariables- Types of outcome measuresTypes of outcome measures
Study SubjectsStudy SubjectsGeneralizing the ResultsGeneralizing the Results
““Research is only interesting to others if Research is only interesting to others if they can apply it to their practice”they can apply it to their practice”
Study SubjectsStudy Subjects
Subjects in the study sample should be Subjects in the study sample should be representative of the population of interestrepresentative of the population of interest
Depending on study different populations Depending on study different populations may yield different results.may yield different results.
- Examples: General population, ED Examples: General population, ED patients, Clinic Patients, Attitudes of patients, Clinic Patients, Attitudes of patientspatients
- Laceration studies, syncope studyLaceration studies, syncope study
Study SubjectsStudy Subjects
Specify the best clinical and demographic Specify the best clinical and demographic characteristics of the study population to characteristics of the study population to best answer questionbest answer question
Appropriate sampling from that target Appropriate sampling from that target populationpopulation
Results = truth in the study Results = truth in the study
Best possible chance to have the results Best possible chance to have the results generalizable.generalizable.
Selection CriteriaSelection CriteriaDefining the Target PopulationDefining the Target Population
Inclusion CriteriaInclusion Criteria
- defines the main characteristics of the defines the main characteristics of the target population – be specifictarget population – be specific
Selection CriteriaSelection Criteria Defining the Target PopulationDefining the Target Population
Exclusion CriteriaExclusion Criteria
- Individuals whose characteristics may Individuals whose characteristics may interfere with the quality of the resultsinterfere with the quality of the results
- Phenomena often not suited for Phenomena often not suited for measurement (e.g. Death)measurement (e.g. Death)
- DichotomousDichotomous
- NominalNominal
- Ordinal – categories have order but no Ordinal – categories have order but no specific numerical or uniform difference specific numerical or uniform difference
Train and certify observersTrain and certify observers
Refining the instrumentsRefining the instruments
Automating the instrumentAutomating the instrument
Repetition (reduces random error)Repetition (reduces random error)
AccuracyAccuracy
““Does the variable actually measure or Does the variable actually measure or represent what it intends to”represent what it intends to”
Assessed by comparison to a “Gold Standard”Assessed by comparison to a “Gold Standard”
Different than precision, but many things that Different than precision, but many things that improve precision improve accuracyimprove precision improve accuracy
A function of systematic errorA function of systematic error- Observer biasObserver bias- Subject BiasSubject Bias- Instrument BiasInstrument Bias
Making Unobtrusive measuresMaking Unobtrusive measures
BlindingBlinding
Calibration of InstrumentsCalibration of Instruments
ValidityValidityAccuracy when there is no “Gold Standard”Accuracy when there is no “Gold Standard”
- Measuring an abstract or subjective Measuring an abstract or subjective phenomena (e.g. – pain, quality of life)phenomena (e.g. – pain, quality of life)
- Content Validity (Face, Inherent or Content Validity (Face, Inherent or sampling validity)sampling validity)
- Construct ValidityConstruct Validity
- Criterion Related Validity (Predictive Criterion Related Validity (Predictive Validity)Validity)
Final ThoughtsFinal Thoughts
An outcome measure should be sensitive An outcome measure should be sensitive enough to determine important clinical enough to determine important clinical differencesdifferencesIt should be associated with only the It should be associated with only the characteristic of interestcharacteristic of interestMeasurements should involve data Measurements should involve data collection that is efficient in time and costcollection that is efficient in time and costEfficiency is improved by increasing the Efficiency is improved by increasing the quality of each item measuredquality of each item measured