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L7 research methods &designs
L7 research methods &designs
L7 research methods &designs
L7 research methods &designs
L7 research methods &designs
L7 research methods &designs
L7 research methods &designs
L7 research methods &designs
L7 research methods &designs
L7 research methods &designs
L7 research methods &designs
L7 research methods &designs
L7 research methods &designs
L7 research methods &designs
L7 research methods &designs
L7 research methods &designs
L7 research methods &designs
L7 research methods &designs
L7 research methods &designs
L7 research methods &designs
L7 research methods &designs
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L7 research methods &designs

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  • 1. Research Methods and Research Designs Ewnetu Firdawek
  • 2. Outline • Definition – Research Method Vs Research Design • Qualitative Research Methods • Quantitative Research Methods • Research Designs – Descriptive Designs – Analytic Designs • Selecting Methods and Designs – Internal vs. External validity ….. the concept of sampling and inference
  • 3. Definition • Methods: – Refer to the way how the required information or data is collected. – Example; through interview, using questionnaires, observations, record reviews, measurements. • Design: – Refers to the overall methodology as to how the study should be undertaken. – It defines the way and the pattern of data collection to be cross- sectional or longitudinal, it states the selection of study units, and sample allocation, it defines the data analysis…
  • 4. Qualitative Research Methods Qualitative research methods utilize – In-depth interview /IDI/ – Focus group discussions /FGD/ – Observations – Record review or Document Analysis • Qualitative data are not countable and can not be expressed in numbers. • Qualitative methods are used to capture individuals feeling, attitude, interest, opinion, and thought.
  • 5. Quantitative Research Methods Quantitative research methods utilize – Structured questionnaires – Measurements • Quantitative data are expressed in the form of counts and other statistical parameters like mean, mode variance, SD, correlation…
  • 6. Research Designs • Quantitative study designs have two broad classification Observational and Experimental Designs with in which there exist a number of study designs. • Observational-investigaters stand apart from events taking place in the study ,they simply observe &record. • Expermental-investigater introduce intervention &observe the event Observational Studies  Descriptive studies  Analytical Studies  Longitudinal  Cross-sectional Studies  Case-Control Studies  Cohort studies Experimental Studies  Randomized Controlled Trials  Non randomized
  • 7. Descriptive Vs. Analytic Studies • Descriptive study designs are limited to description of the subject under consideration in a particular population and are the first step in any study. • However pure descriptive studies are rarely done, descriptive data is presented usually for the purpose of health statistics or comparison of population health status. • Analytical study designs goes further by analyzing the relationship between the interest variable and other factors.
  • 8. Cross-sectional Study Design • Measurements are made on a single occasion • Are also called prevalence studies. • Used to measure the prevalence of a particular health condition at a point in time. • Both the exposure and effect are measured at the same time, and difficult to present whether the effect or the exposure precede. • Determining casual relationships is difficult. • Used to generate hypothesis.
  • 9. Cross-sectional… • Very useful in investigating the cause of sudden outbreaks or health conditions and compare fixed exposure characters like sex, blood group. • Used to assess health care needs of a population. • Used to provide trend estimates when done in a representative and repeated periods of time in a particular population for the same objectives. • Conducted in national level to estimate the health status of the population. Example; DHS
  • 10. Longitudinal study • Measurements are made over a period of time • May retrospective or prospective • In retrospective study investigators study past and present events • In prospective study investigators follow subjects for future event
  • 11. Case-Control Study Design • It is a popular retrospective study, since the investigator is looking backward from the disease to a possible cause. • Used to investigate the cause of rare diseases or health outcomes. • Involve people with the health outcome (referred as cases) and those with no health outcome or the disease (referred as controls). • Compare the occurrence of the possible cause in cases and in controls. • The investigator collects disease occurrence at one point in time and the exposure at previous point of time.
  • 12. • The association of an exposure and disease in case control study is measured by calculating the Odds Ratio. • It is the ratio of the odds of exposure among cases to the odds of exposure among controls. Case-control study designs flow chart
  • 13. Cohort Study Designs • Also called follow-up or Incidence rate studies. • The study begins with a group of people who are free of disease and who are classified into subgroups according to exposure to a potential cause of a disease or outcome. • Variables of interest are specified and measured and the whole cohort is followed up to see how the subsequent development of new cases of the disease or the outcome differs between the groups with and without exposure. • Start with healthy people and look for the occurrence of the outcome.
  • 14. Cohort…. • Cohort studies are therefore longitudinal studies. • Provide best information on the causation of an outcome and the risk of developing an outcome or disease. • Expensive compared with other study designs. • Relative risk is measured to estimate the incidence of the outcome among the exposed groups.
  • 15. Cohort…. • Ex-study by bradford and rechard to investigate relation ship between smoking &lung cancer • Followed 40,000 british docters who were devided in to four cohort:non smokers,light moderate and heavy smokers. • Death was the out come they recorded • Used both all cause death(any death) and cause specific death • Finding-more death from all cause &from lung cancer in smokers
  • 16. Cohort study designs flow chart
  • 17. Experimental Study Designs • Are also called interventional studies. • Attempt to change a variable in one or more groups of people. • Here the investigator manipulates the status of exposure on subjects, then the effects of the intervention are measured by comparing the outcome in the experimental group with that in a control group. • Ethical considerations have paramount importance. • Informed consent has to be taken.
  • 18. Experimental study designs flow chart
  • 19. Randomized Controlled Trials • Usually used to study the effect of a particular intervention, treatment, for a specific disease or outcome (clinical trail) • Subjects are randomly allocated to intervention and control groups, outcomes are then compared. • Random allocation is made to ensure the comparisons groups are equivalent . • Any difference between groups is considered as chance occurrence and unaffected by the conscious or unconscious biases of the investigators.
  • 20. Randomized controlled trials flow chart

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