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3.research design
 

3.research design

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Contains Research methodology study material, might be useful to medical and paramedical UG and PG students pursuing Research

Contains Research methodology study material, might be useful to medical and paramedical UG and PG students pursuing Research

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    3.research design 3.research design Presentation Transcript

    • Research Design D.A. Asir John Samuel, BSc (Psy), MPT (Neuro Paed), MAc, DYScEd, C/BLS, FAGE
    • Meaning of research design• The arrangement of conditions for collection and analysis of data in a manner that aims to combine relevance to the research purpose with economy in procedure Dr. Asir John Samuel (PT), Lecturer, ACP 2
    • Need for research design• Smooth sailing of various research operations• Yielding maximal information• Minimal expenditure of effort, time & money• Plan for house• Advance planning of methods to be adopted for collecting relevant data and techniques to be used in analysis Dr. Asir John Samuel (PT), Lecturer, ACP 3
    • Need for research design• Efficient and appropriate design must be prepared before starting research operation OR futile• Organize ideas in a form• Possible to look for flaws & inadequacies• Need for providing comprehensive review Dr. Asir John Samuel (PT), Lecturer, ACP 4
    • Features of good research design• Flexible• Appropriate• Efficient• Economical• Minimises bias• Maximises the reliability of collected data and analysed Dr. Asir John Samuel (PT), Lecturer, ACP 5
    • Features of good research design• A research design should consider,- Means of obtaining information- Objective of the problem to be studied- Nature of the problem to be studied- Availability of time and money• Emphasis on discovery of ideas and insights• Hypothesis if casual relationship b/w variables Dr. Asir John Samuel (PT), Lecturer, ACP 6
    • Different research designs Study designs Observational Experimental Descriptive Analytical RCT Non-RCT Cross- Case controlCase report Case series sectional Cohort study study Dr. Asir John Samuel (PT), Lecturer, ACP 7
    • Case report• Studies describing the characteristics of a single patient Dr. Asir John Samuel (PT), Lecturer, ACP 8
    • Case report-merits• Record unusual medical occurrences and can give the first clues in identification of a new disease or adverse effects of an exposure• Only means of surveillance for rare clinical events• Serve to elucidate the mechanism of disease and treatment Dr. Asir John Samuel (PT), Lecturer, ACP 9
    • Case report-Demerits• Cannot be used to test for the presence of valid statistical association because it is based on the experience of one person Dr. Asir John Samuel (PT), Lecturer, ACP 10
    • Case series• Studies describing the characteristics of a group of patients with similar diagnosis• Collection of 5 & more cases Dr. Asir John Samuel (PT), Lecturer, ACP 11
    • Case series-merits• Helps in formulating a useful hypothesis regarding risk factors of disease or identifying a new disease or outcome of new treatment• Informative for very rare disease with few established risk factors• May suggest the emergence of a new disease or epidemic Dr. Asir John Samuel (PT), Lecturer, ACP 12
    • Case series-DemeritsCannot be used to test for the presence of validstatistical association due to absence of acomparison group Dr. Asir John Samuel (PT), Lecturer, ACP 13
    • Cross-sectional studies• Single examination of a cross section of population at one point of time• Helps to generate a hypothesis• Used to investigate non fatal diseases• Both exposure and outcome (disease) are determined simultaneously for each subject• Provide information about the frequencey or characteristic of disease Dr. Asir John Samuel (PT), Lecturer, ACP 14
    • Cross-sectional studies-Merits• Provide information about the frequency of an attribute and potential risk factors• Helps to generate a hypothesis• Can give a good picture about the health care needs of the population at the point of time• Can be used to investigate multiple exposure and multiple outcome• Suitable for chronic cases Dr. Asir John Samuel (PT), Lecturer, ACP 15
    • Cross-sectional studies-Demerits• Difficult to establish the time of sequence of events• They are not suitable to investigate rare diseases, rare exposure or disease of short duration• Being based on prevalent rather than incident cases• Limited value to investigate etiological relationship Dr. Asir John Samuel (PT), Lecturer, ACP 16
    • Case control study• Type of analytical study• By observation and analysis• Retrospective evaluation to determine who was exposed and who was not exposed – retrospective study Dr. Asir John Samuel (PT), Lecturer, ACP 17
    • Case control study• To examine the possible relation of an exposure to certain disease- Identify the individual having the disease – case- Individual don’t have the disease – comparison purpose Dr. Asir John Samuel (PT), Lecturer, ACP 18
    • Case control studyFactor (s)Present individuals with disease TIME Direction of enquiryAbsent individuals w/o disease Dr. Asir John Samuel (PT), Lecturer, ACP 19
    • Case control study4 basic steps in conducting a case control study,1. Selection of cases and controls2. Matching3. Measurement of exposure4. Analysis and interpretation Dr. Asir John Samuel (PT), Lecturer, ACP 20
    • Case control study – Merits• Quick, less expensive• Well suited for disease with long latent period• Optimal for evaluation of rare diseases• Can study etiological factors for a single disease• Requires small sample than a cohort study• No attrition (drop outs) problem• Ethical problems are minimal, no risk to subjects Dr. Asir John Samuel (PT), Lecturer, ACP 21
    • Case control study- Demerits• More prone to bias• Selection of appropriate control group may be difficult• Inefficient for evaluation of rare exposure• Cannot directly measure incidence, can only estimate relative risk Dr. Asir John Samuel (PT), Lecturer, ACP 22
    • Cohort study• Forward looking study• Prospective study• Incidence study• Longitudinal study• There is regular follow up over a period of time Dr. Asir John Samuel (PT), Lecturer, ACP 23
    • Cohort study Factor (s)Individuals exposed Present TIME Direction of enquiryindividuals unexposed Absent Dr. Asir John Samuel (PT), Lecturer, ACP 24
    • Cohort study• Proceeds from cause to effect• Exposure has occurred when the study is initiated, but the disease has not occurred Dr. Asir John Samuel (PT), Lecturer, ACP 25
    • Cohort• A group of people who share a common characteristic or experience within a defined time period• Cohort must be free from disease under study• Both groups (study cohort & control cohort) should be equally susceptible for the disease under study• Should be comparable in all possible variables Dr. Asir John Samuel (PT), Lecturer, ACP 26
    • Cohort study• Elements of a cohort study,1. Selection of study subjects2. Obtaining data on exposure3. Selection of comparison group4. Follow-up5. Analysis Dr. Asir John Samuel (PT), Lecturer, ACP 27
    • Cohort study - Merits• Incidence can be calculated• Examines multiple effects of a single exposure• Provides direct estimate of relative risk• Minimizes bias• Dose-response ratios can be calculated• Elucidates temporal relationship b/w exposure & disease Dr. Asir John Samuel (PT), Lecturer, ACP 28
    • Cohort study - Demerits• Inefficient for rare diseases• Expensive and time consuming• Involves large sample size• Alters people behaviour• Changes in standard methods or diagnostic criteria of disease over prolonged follow-up Dr. Asir John Samuel (PT), Lecturer, ACP 29
    • RCT• Basic steps in conducting a RCT,1. Drawing up a protocol2. Selecting reference & exp. Group3. Randomization4. Manipulation or intervention5. Follow-up6. Assessment of outcome Dr. Asir John Samuel (PT), Lecturer, ACP 30
    • Select suitable population Select suitable sample Exclusions RandomizeExperimental Control group group Intervention & follow-upDr. Asir John Samuel (PT), Lecturer, ACP 31
    • SACKETT LEVEL OF EVIDENCE Dr. Asir John Samuel (PT), Lecturer, ACP 32
    • Randomization• Simple randomization• Block randomization• Stratified randomization• Unequal randomization Dr. Asir John Samuel (PT), Lecturer, ACP 33