" Observational designs are nonexperimental, quantitative designs. In contrast to experimental designs in which the investigator manipulates the independent variable and observes its effect, the investigator conducting observational research observes both the independent and dependent variables. In observational studies, variation in the independent variable may be due to genetic endowment, self-selection, or occupational or environmental exposures" (Meininger, 2017).
There are three types of observational study designs:
In a case-control study,
" participants are selected and categorized on the basis of the dependent variable (the outcome of interest). The purpose of the study is to test hypotheses about factors in the past (independent variables) that may explain the outcome" (Meininger, 2017).
With a cohort study,
"participants are measured or categorized on the basis of the independent variable and are monitored over time to observe occurrence of the dependent variable. In a cohort study, it is established at the outset that subjects have not already exhibited the outcomes of interest (dependent variable)" (Meininger, 2017).
And with a cross-sectional study,
"participants are observed only once, offering a 'snapshot' of the characteristics of interest at that particular moment" (Research Methods, 2008).
Unlike other types of studies like randomized controlled trials and systematic reviews, there are no specific limiters for these types of study designs. The best way to find these types of articles is to add a keyword of the study type to your search string. See examples below:
heart disease AND cohort
diabetes AND case-control
hypertension AND cross-sectional
There are also a few things that you can do in specific databases that may increase the chance to find these types of studies. Below are two databases that will allow you to limit your search results to case reports, case studies, or observational studies only.
To find these types of observational studies in Medline, follow the steps below:
1. Enter the database through the link above. This will take you directly to the advanced search page for this database. Enter your keyword (s) into the search boxes.
2. Scroll down to the Limit Your Results section. This is where you can add filters to your search to tell the database that you only want articles that fit specific criteria.
3. Locate the Publication Type menu, and select either Case Report, Case Study, or Observational Study. After you have your results, make sure to read through the article abstracts to see what type of study design the researchers are using because it's not a guarantee that the database will only generate these types of studies.
To find these types of observational studies in PubMed, follow the steps below:
1. Enter the database through the link above.
2. Search your topic by entering your keywords into the search box and hitting search.
3. Select Additional Filters to the left of the search results to see all the filters available.
4. This will generate a popup box where you can click on Article Type and choose either Case Reports or Observational Study.
Note! With any of these searches, you will need to limit to full text to get articles immediately available to you.
Meininger, J. C. (2017). Observational research designs. In J. Fitzpatrick (Ed.), Encyclopedia of nursing research (4th ed.). Springer Publishing Company.
Research methods and measurement and: Cross-sectional. (2008). In I. P. Albery, & M. Munafo, Key concepts in health psychology. Sage UK.
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