Question: This module discussed the importance of selecting a suitable study des

Question

Question:

This module discussed the importance of selecting a suitable study design and methods for data analysis based on a research question. For each of the following research questions. state the type of study described by each of the following paragraphs. Also explain your reasoning for why you chose the study type.

To investigate the relationship between egg consumption and heart disease, a group of patients admitted to a hospital with myocardial infarction were questioned about their egg consumption. Another group of patients admitted to a fracture clinic and matched on age and sex with the first group were also questioned about their egg consumption using an identical protocol.

To investigate the relationship between certain solvents and cancer, all employees at a factory were questioned about their exposure to an industrial solvent, and the amount and length of exposure measured. These subjects were regularly monitored, and after 10 years a copy of the death certificate for all those who died was obtained.

A survey was conducted of all nurses employed at a particular hospital. Among other questions, the questionnaire asked about the grade of the nurse and whether or not she was satisfied with her career prospects.

To evaluate a new school (i.e., approach) for treating back pain, patients with lower back pain were randomly allocated to either the new school or to conventional occupational therapy. After 3 months, they were questioned about their back pain, and observed lifting a weight by independent monitors.

A new triage system has been set up at the local Accident and Emergency Unit. To evaluate this new system, the waiting times of patients were measured for 6 months and compared with the waiting times over a comparable nearby period.

The Tumor Registry in a certain US state was used to identify all primary cases of bladder cancer in the state during a given period. These cases were compared to a sample of non-cases from the same state that have been matched on age and time of diagnosis. All subjects or their surviving relatives in both groups were interviewed to collect information on saccharin consumption and other known risk factors for bladder cancer.

In the Hanford study of nuclear power workers (1977), 3500 certified deaths occurred among plant workers between 1944 and 1972. Among these deaths, a significantly greater proportion of workers exposed to low levels of ionizing radiation than unexposed workers had died of RES (reticuloendothelial system) cancers.

Explanation / Answer

1. Matched case controlled study: A study that compares patients who have a disease or outcome of interest (cases with myocardial infartion here) with patients who do not have the disease or outcome (controls who are normal with only fractures) and looks back retrospectively to compare how frequently the exposure to a risk factor is present in each group to determine the relationship between risk factor and the disease.

2.Cohort study: A study in which subjects are initially disease free, are followed up over a period of time. Some will be exposed to some risk factor (industial solvent in this case). The outcome may be death and we are interested in relating the risk factor (solvent here) to cause of death.

3. Cross sectional study: common studies that include surveys to examine prevalence of disease. Studies with questionnaires are also cross secttional stuies.

4. Randomized controlled trial: these are quantitative, comparitive, controlled experiments in which investigators study two or more interventions in a series of patients who receive them in random order.

5. Quasi experimental study: this study can be used in this case to estimate the casual impact of an intervention on its target population without random assignment.

6. Retrospective study/ historical cohort study: looks backwards and examines possible risk factors and exposure to them.

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