Effectiveness of Studies Used in Epidemiology
A premise of epidemiology is that health outcomes are not random occurrences within a population, but
are linked to particular risk factors and diseases. Epidemiologists utilize a range of study design methods
to evaluate evidence-based associations to understand and improve health outcomes. Use the specific
Excel worksheets, located in the “Excel Study Design Workbook, to complete this assignment.
Part 1: Study Design Comparison:
Using the “Study Design Comparison Worksheet,” compare and contrast the characteristics of the
different types of study design types discussed in this course. You will be able to use this as a reference
throughout the program.
Part 2: Article Comparison:
Consider an area of interest that you want to explore as a potential topic for your Epidemiological
Profile project. Search for two articles that fit any two of the four study designs (randomized trial,
cohort, case-control, and cross-sectional) pertaining to the interest area you chose. Review the articles
provided in the “Study Design Resource Document” to practice identifying articles for each study design.
(Do not use the actual articles listed in the “Study Design Resource Document” for this assignment.)
Complete the “Article Comparison Worksheet” to compare the study design characteristics in each of
your two articles. Include details of any gaps in the characteristics or identify if information is missing.
| PUB 540 – Study Design Comparison Worksheet | ||||
| Randomized Trial | Cohort Study | Case-Control Study | Cross-Sectional Study | |
| Type: Descriptive or Analytic | Analytic | Analytic | Analytic | Descriptive |
| Participant selection criteria (by exposure status, outcome status, randomized, or other) | Participation is on the basis of convenient sampling using census based estimates of a population or target population. Two groups are used and selection is randomised with the outcome being the variable being tested. | The participants are selected to fit into two groups which is based on the exposure status of the individuals selected. One group is exposed while the other is less exposed or not exposed at all. | The selection criteria is based on the individuals who have been exposed with selected outcomes involved. | The participants are selected from a pool of individuals who have been exposed and are likely to produce a given outcome. It measures the exposure and outcome of the given target population. |
| Observation type (Prospective, retrospective, or single time point) | Observation type in randomised trial studies is prospective and forms the basis of evidence based practices. They are conducted for a long period of time. | The observation method utilised are prospecive and repreospect which involves exposure and outcomes of a condition among the target population. | Case Control studies are retrospective and are alao apply a single time point incoporated in the design. | The observation type is prospective, retrospective and single time point as it involves the use of exposures to determine the varibale outcome in the given target population. |
| Data Sources (primary data, surveys, secondary data, medical records, other) | Primary data and surveys provide the data in radomised trials as the use of secondary data introduces biases to the study. | Primary data, surveys and medical records are used to provide the data in Cohort studies. It also has used secondary data but to a limited extent. | Secondary data, surveys, primary data and medical records are used as data sources. | Primary data, secondary data, medical records, and surveys are used to provide information in the studies. |
| Measures of association (prevalence/odds ratios, incidence/relative risk) | Incidence and relative risk are used as the measures of association among exposure and outcomes | Incidence/relative risk are used to bring out association measures in the study | Incidence /relative risks are the associations measures in case control studies. It also may employ the use of prevalence/odds ratios. | The measures of association include prevalence/odd ratios for exposure and outcomes of a condition. |
| Major strengths | Elimination of selection bias, provides a comparison against other treatment trial studies available, increases statistical reliability, and reduction of confounding factors. | Defines the sequence of from exposure to outcome of a disease, brings out the incidence rate, multiple effects from one single exposure can be examined, and elimination of selection bias. | Used in long latency period conditions, low cost to conduct the study, mimimum time used in the study, required for dynamic populations with followup requirements. | Quick and easy to conduct, relatively cheap, accurate as it represents past exposures, data collection is done once, generation of hypothesis for future analytical studies, study of multiple outcomes and leads to adequate public health planning. |
| Major weaknesses (sources of bias, etc.) | Selection bias may be brought out by the statistical data, efficacy studies are not widely applicable, while the efficiency ones are expensive, logistical demand is high,and ethical limitations are applicable. | Differential loss due to biases, poor quality data, rare and long latency dieases are not accurately measured, large number of target population followup for a long duration, and expensive to conduct. | Do not show the incidence risks and rates, observational bias may occor due to gathering of exposure information, inefficiency in rare disease occorences, and they are subjected to selection bias. | One cannot define whether disease or its outcome came first, data is a measure of determinant of survival, prevalence rates rather than incidence rates, not suitable for short duration studies, and difficults to measure associations. |