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Study Designs
Published in Abhaya Indrayan, Research Methods for Medical Graduates, 2019
A good research strategy provides conclusions with minimal error within the constraints of funds, time, personnel, and equipment. A useful strategy that works in some analytical studies is comparison of characteristics of a population with a high incidence with those of a population with a low incidence. Thus, the factors contributing to the difference can be identified. This is called an ecological study. Frequencies and rates in different segments of the population can also be compared. For example, Korkeila et al. [10] compared the frequency of use of antidepressants and the suicide rate in the population of Finland, and found an inverse relationship in the two. You can see that, in an ecological study, only the group characteristics are studied and individuals as such have no role.
Environmental Exposures and Reproduction *
Published in Michele Kiely, Reproductive and Perinatal Epidemiology, 2019
Up to this point in time, a majority of the studies of environmental exposures have used an ecologie study design. In an ecological study, exposure is assigned to groups by residential history or some other group characteristic. Outcome is expressed as rates of the outcome within broad exposure groupings. Such studies can be done on a limited budget, and in a shorter time frame than a more indepth study. However, the results are of more limited use than other study designs due to the inherent misclassification. This misclassification results from variation in individual exposures (e.g., environmental toxicants, smoking patterns, medications, and occupational exposures) and characteristics (e.g., basic demographic data) which are typically not determined21 (e.g., see References 22 to 23). The term “semi-ecologic” has been suggested24 for those studies where individual data on the outcome of interest are identified (rather than group rates), and while the exposure is still based on some group characteristic (e.g., see References 25-27). Ecologie and semi-ecologic studies aid in the generation of hypotheses requiring further study, and the identification of appropriate groups for further examination.
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Published in Filomena Pereira-Maxwell, Medical Statistics, 2018
An error that arises when measuring an association in an ecological study. This error or distortion can be in the form of a spurious association (due to difficulties in adequately controlling for the presence of confounding), or it can be in the form of dilution of association (due to the use of ‘averaged’ measurements at the population level, and proxy measures for exposure and disease). See ALTMAN (1991), ROTHMAN (1986). See also regression dilution bias.
A single-case experimental design investigation of collaborative goal setting practices in hospital-based speech-language pathologists when provided supports to use motivational interviewing and goal attainment scaling
Published in Neuropsychological Rehabilitation, 2022
Priya Kucheria, McKay Moore Sohlberg, Wendy Machalicek, John Seeley, David DeGarmo
Contextual Factors. Compromises in study validity were a direct result of our goal to conduct a highly ecological study in the natural hospital setting. Implementation science encourages early partnering with stakeholders, particularly clinicians, when evaluating interventions (Sohlberg et al., 2015), which while important, can be challenging. For example, the institution required that the study duration, number of sessions, and training schedules be disclosed in advance which made it difficult to ensure a stable baseline. Another barrier that prevented adherence to the gold standard of conducting a concurrent multiple-baseline design was managing clinicians’ work schedules, professional obligations, with the incoming caseload for scheduling evaluations. Clinicians had varying workdays, work demands that would often require them to work in other units of the hospital, differences in vacation times that did not consistently coincide with times when the hospital had higher census and more flexibility to schedule evaluations. Scheduling of evaluation sessions was largely dependent on clinician and caseload availability, making it impossible for all clinicians to begin the study simultaneously.
State health policies and interest in PrEP: evidence from Google Trends
Published in AIDS Care, 2022
Bita Fayaz Farkhad, Mohammadreza Nazari, Man-pui Sally Chan, Dolores Albarracín
Our study has limitations. First, our data sources did not allow us to investigate the effects across population characteristics. This limitation is important because evidence suggests that PrEP awareness is not uniform across different populations (Finlayson et al., 2019). Second, Google searches are prone to bias as i) they aggregate the searches without distinguishing how many queries each user has made and who performed the searches, ii) certain groups have lower access to the internet, iii) users may restrict their location access in privacy settings, iv) they represent only searches done using the Google engine, v) searches may be associated with inaccurate geolocations due to using virtual private networks, and vi) they include neither misspelling nor typographical errors. Although the Google searches may not be representative of the entire population, changes in search behavior may still track changes in the general population, an idea that prior research has supported (Mellon, 2014). Third, despite controlling the number of men who have sex with men deems desirable, this omission is unlikely to bias our results as differences across states are captured by the inclusion of fixed effects. Finally, this is an ecological study that may not fully control for time-varying differences across states. Since state policy decisions are not random, our findings may not imply causality. However, supplementary analysis suggests that the same pattern was not present for control keywords, which suggests that our findings are unlikely to be driven by unobserved confounders.
Characterizing environmental asthma triggers and healthcare use patterns in Puerto Rico
Published in Journal of Asthma, 2020
Lillianne M. Lewis, Maria C. Mirabelli, Suzanne F. Beavers, Caitlin M. Kennedy, Jennifer Shriber, Dorothy Stearns, Jonathan J. Morales González, Marimer Soto Santiago, Ibis Montalvo Félix, Krystel Ruiz-Serrano, Emilio Dirlikov, Matthew J. Lozier, Kanta Sircar, W. Dana Flanders, Brenda Rivera-García, Jessica Irizarry-Ramos, Benjamin Bolaños-Rosero
Studies examining asthma-related healthcare use in Puerto Rico are limited in scope and number (9–14). Improving our understanding of the reasons for higher asthma morbidity is important for addressing asthma disparities. We conducted this study to better understand asthma morbidity in Puerto Rico by examining environmental asthma triggers and characterizing asthma-related healthcare use via examination of insurance claims. Similar to other public health, environmental, and air pollution studies (15–20), we used an ecological study design, linking health and environmental data, coupled with a time-series statistical regression approach to gain insights into causal associations.