# Quantitative Methods.pptx

2 de Jun de 2023
1 de 27

### Quantitative Methods.pptx

• 1. Dr. Khem R. Sharma, Assistant Professor School of Public Health & Community Medicine, BPKIHS
• 2. To describe the burden of disease or prevalence of risk factors, health behaviors, or other characteristics of a population that influences the risk of disease To determine the causes or risk factors for illness To determine the relative effectiveness of interventions 2
• 3. Medical Research methods include scientific ways to distinguish facts from fiction in broadly two categories: 1) Quantitative research methods: emphasize objective measurements (numerical data) and analysis of poll, questionnaire data or manipulating pre-existing statistical data using different computational techniques. 2) Qualitative research methods: focused more on discovering underlying meanings and patterns of relationships in a manner, that does not involve mathematical models. Example: Focus Group Discussion 3
• 4.  Quantitative research is a systematic investigation of assembling quantifiable data and performing statistical, mathematical or computational techniques to present it.  The goal in conducting quantitative research study is to determine the relationship of one entity [independent variable] with another [dependent or outcome variable] within a population.  Quantitative research designs are either descriptive [subjects usually measured once & establishes only associations between variables] or experimental [subjects measured before and after a treatment & establishes causality]. 4
• 5.  Structured tools: Questionnaires are used to gather quantitative data which helps in collecting in-depth and accurate information from the survey respondents.  Sample size: Quantitative research is conducted based on significant sample size that represents the target population, with the use of appropriate sampling methods to meet the research objectives  Prior studies and preparation: Adequate groundwork needs to be done before starting the study as all aspects of the study needs to be carefully designed before data collection ensues. 5
• 6.  Quantitative data: in the form of numbers and statistics represented by tables, charts, graphs etc. makes it easy to understand the information  Generalization of results: Results of the research can be generalized to a subgroup or even the entire population to take appropriate actions for improvement.  The study can usually be replicated or repeated, given its high reliability. 6
• 7. Quantitative methods have an objective approach to studying research problems as a consequence, the results of quantitative research may be statistically significant but may be humanly insignificant.( Biologically not plausible) Though more efficient and able to test hypotheses, it may miss contextual detail; Uses a static and rigid approach and so employs an inflexible process of discovery; Results provide less detail on behavior, attitudes, and motivation; 9
• 8. I. Observational Studies a) Descriptive (case study, case series, cross-sectional) b) Analytical (cross-sectional, case-control, cohort , ecological studies) II. Experimental Studies a) Randomized Control Trial (RCT/ Clinical Trials) b) Field Trials (Healthy people as units) c) Community trials (Communities as units of study) 10
• 9. Observational studies allows nature to take its own course; the investigator keeps measuring, but does not intervene. Descriptive studies are limited to description of the problem that exists in that population Analytical studies go one step further and analyses the relation between the outcome variable and various factors implicated in its occurrence. Experimental/Intervention studies involve active interventions to change the progression of a disease/event. 11
• 10. The first phase of an epidemiological investigation concerned with observing the distribution of disease or health-related characteristics in human populations & identifying the factor with which the disease seems to be associated. Such studies basically ask the questions. a) When is the disease occurring ? - time distribution b) Where is it occurring ? - place distribution c) Who is getting the disease? - person distribution 12
• 11. Analytical Studies interest is the individual within the population to test hypothesis inference is not to individuals. but to the population from which they are selected. Answer why and how Descriptive Studies • look at entire populations • to formulate hypothesis • gives person, time & place status of Health Problems • Answer what, who, where, and when 13
• 12. Simplest form of an observational study Based on a single examination of a cross-section of population at one point in time - the results of which can be projected on the whole population (Photograph) Usually Descriptive-Analytical when two groups are compared Provides very little information about the natural history of disease or about the rate of occurrence of new cases (incidence). 14
• 13.  Common first approach to test causal hypothesis  Three distinct features: a) Both exposure & outcome have occurred before the start of study b) Study proceeds backwards from effect(outcome) to cause (exposure) c) Uses a control/ comparision group to support or refute an inference  To study rare diseases  To study multiple exposures that may be related to a single outcome 15
• 14. 16
• 15. 1) Selection of cases and controls: suitable controls may present difficulties Sources: Case(hospital/gen population) Controls- (hospital/relatives/neighbor hood/gen popn) 2) Matching to ensure comparability between cases and control but controls should free from the disease under study.  Process by which controls are selected such that they are similar to cases with regard to certain pertinent selected variables (e.g., age, gender etc) which are known to influence the outcome of disease and which if not adequately matched for comparability, could confound the results (eg: Alcohol in esophageal cancer VS cig). 17
• 16. 3) Measurement of exposure: Definitions and criteria of exposure should be the same and information about exposure should be obtained in precisely the same manner for both cases and controls  obtained by interviews/questionnaires or studying past hospital, employment records etc. of cases 4) Analysis: to find out- a) Exposure rates among cases & controls to the suspected factor + b) Estimation of disease risk associated with exposure (Odds Ratio) 18
• 17.  Measure of the strength of the association between risk factor and outcome.  cross product of the 2 X 2 table  OR= ad/bc  Odds ratio is based on three assumptions: 1) the disease being investigated must be relatively rare 2) the cases must be representative of those with the disease, & 3) The controls must be representative of those without the disease.  If a race horse runs 100 races and wins 25 times and loses the rest, the probability of winning is 25/100 = 0.25 or 25%, but the odds of the horse winning are 25/75 = 0.333 or 1 win to 3 loses. 19
• 18. What is a cohort? -Well-defined group of people who share a common characteristic or experience within a defined time period (e.g., age, occupation, exposure to a drug or vaccine, pregnancy etc). Example: Those born in 1990 form the birth cohort of 1990 What are other examples of cohorts? 20
• 19. Longitudinal study, follow-up study Participants classified according to exposure status and followed-up over time to ascertain outcome Can be used to find multiple outcomes from a single exposure Appropriate for rare exposures or defined cohorts Ensures temporality (exposure occurs before observed outcome) 21
• 20. 22
• 21. COHORT STUDY The distinguishing features of cohort studies are : 1) the cohorts are identified prior to the appearance of the disease under investigation 2) the defined study groups are observed over a period of time to determine the frequency of disease among them 3) the study proceeds forward from cause to effect. 23
• 22. 1) when there is good evidence of an association between exposure and disease as derived from clinical observations and supported by descriptive and case control studies 2) when exposure is rare but the incidence of disease high among exposed. (eg: hirosima nuclear disaster/Bhopal gas) 3) To learn about multiple outcomes due to a single exposure (eg: Health effects of a nuclear power plant accident) 4) when attrition of study population can be minimized e.g., follow- up is easy, cohort is stable, cooperative and easily accessible 5) when ample funds are available. 24
• 23.  Three types of cohort studies have been distinguished on the basis of the time of occurrence of disease in relation to the time at which the investigation is initiated and continued : 1) Prospective cohort studies: Eg - Doll & Hill, Framingham Heart Study 2) Retrospective cohort studies: Eg: study of lung cancer in uranium miners 3) Combination of retrospective and prospective cohort studies: The cohort is identified from past records, assessed to date for the outcome and the same cohort is followed up prospectively into future for further assessment of outcome. 25
• 24. It is a direct measure (or index) of the "strength" of the association between suspected cause and effect. A RR of one indicates no association while RR of 2 indicates that the incidence rate of disease is 2 times higher in the exposed group as compared with the unexposed RR = Incidence of disease (or death) among exposed Incidence of disease (or death) among non-exposed 26
• 25. The difference in incidence rates of disease (or death) between an exposed group and non-exposed group expressed as a percentage. Attributable risk indicates to what extent the disease under study can be attributed to the exposure Population Attributable Risk (PAR) provides an estimate of the amount by which the disease could be reduced in that population if the suspected factor was eliminated or modified. 27
• 26. Experimental research studies compare the effectiveness of medical treatments, management & prevention strategies, and other medical or public health interventions. Design is very similar to that of a prospective cohort study- intervention is present. Investigator assigns the exposure status in clinical trials, while subjects' genetics, behaviors, and life circumstances determine their exposures in a cohort study 28
• 27. 29