For the following name the unit of analysis and identify the study design (ecolo
ID: 115801 • Letter: F
Question
For the following name the unit of analysis and identify the study design (ecologic, cross-sectional, case-control, historical cohort or prospective cohort study).
a) A total of 3,044 American participants aged 19 or older completed a 24-hour dietary recall and had their blood pressure taken as part of an extensive health interview and examination. Researchers wished to examine associations between intakes of sugar and sugar-sweetened beverages and the prevalence of hypertension in this representative sample.
b) A total of 825 insulation workers employed between 1951 and 1955 were identified from the personnel records of three large insulation manufacturing plants in the southeastern U.S. in 1995. During the period 1951-1995, 26 deaths from lung cancer were discovered among the workers. Only six lung cancer deaths, however, were reported among a comparable group of 700 coworkers who did not work with insulation during the same period. The investigators had postulated that exposure to the insulation material increases the risk of lung cancer.
c) A study was conducted of the history of physical activity among men diagnosed with Type II Diabetes Mellitus as compared to those without diabetes.
d) Prostate cancer mortality rates in 1986 from 41 countries were compared with national tomato supply values in 1985 from the same countries to determine the relationship between average per capita tomato consumption and death due to prostate cancer.
e) Questionnaires were mailed to every 10th person listed in the city telephone directory. Each person was asked to provide his or her age, sex, and smoking habits and to describe the presence of any respiratory symptoms during the preceding seven days.
Explanation / Answer
a) In this 3,044 American participants were selected hence it is a group unit of analysis, the design here is of case control study because case-control studies were traditionally referred to as retrospective studies, due to the nature of the study design and execution. In this study design, researchers identify study participants based on their case status, i.e. diseased or not diseased. Quantification of the number of individuals among the cases and the controls who are exposed allow for statistical associations between exposure and outcomes to be established.
b) Here the uint of analysis is social organizations, this is retrospective cohort studies because it begin with a cross-sectional study to categorize exposure and identify cases. Exposures are then measured based on records created at that time. Additionally, in an ideal retrospective cohort, case status is also tracked using historical data that were created at that point in time. Occupational groups, particularly those that have regular surveillance or certifications.
c) Here the uint of analysis is group wise, the study design is Cross-sectional study design. These studies consist of assessing a population, as represented by the study sample, at a single point in time. Cross-sectional study samples are selected based on their exposure status, without regard for their outcome status. Outcome status is obtained after participants are enrolled. Ideally, a wider distribution of exposure will allow for a higher likelihood of finding an association between the exposure and outcome if one exists. Cross-sectional studies are retrospective in nature. An example of a cross-sectional study would be enrolling participants who are either current smokers or never smokers, and assessing whether or not they have respiratory deficiencies.
d) Here the uint of analysis is social artifacts. This is an example of Ecological study design. This study design compares clusters of people, usually grouped based on their geographical location or temporal associations. Ecological studies assign one exposure level for each distinct group and can provide a rough estimation of prevalence of disease within a population. Ecological studies are generally retrospective. An example of an ecological study is the comparison of the prevalence of obesity in the United States and France.
e) Here the uint of analysis is individuals(most common type of analysis). The study design here is again Cross-sectional study design.