1. The study of populations or subgroups is very important to policymakers because, they gain from the results of such studies more insights into the topic being explored. As a result, it helps them to develop policies that address the main issue observed in the study. For example, if the results of a study identifying social factors that lead people to start smoking indicate that a certain percentage of smokers were influenced by friends or peers, policies can be put in place to prevent smoking in public.
2. An experimenter would choose to use experimental research if the research is at risk of being faced with factors beyond the controls of a cohort research. In cohort studies, the results are more easily affected by the factors that investigators may have little control over. Therefore, cohort studies are more likely to be affected by issues of legitimacy.
3. Descriptive studies are studies that describe the topic of a study. In the study of disease, descriptive studies characterize the disease amount and distribution within a population. In descriptive study, the disease is evaluated in terms of persons, place and time. Descriptive studies are, therefore, central to epidemiology because the aspects studied in descriptive studies will fully demonstrate the epidemiological information of the particular diseases.
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4. By describing the disease in terms of place, person and time, these studies provide three dimensional descriptions of the disease distribution (among people, in different regions, and at different times). Since epidemiology is the study of disease distribution, then the descriptive studies appear to be the most relevant in the study of disease. The results of descriptive studies may thus be used to explore the preventive measure of the disease by focusing on the time, person and place aspects of the disease.
For a health problem like malaria, descriptive study may be applied. The disease can be described in terms of place, person and time. In terms of place, malaria is more common in the tropics because the insect vector of malaria (female anopheles mosquito) survives well in the tropical rain forests and grasslands. Even within this locality, the disease is common among the communities living near water bodies, especially lakes, and those in the bushy and littered environment. Mostly, this is because mosquitoes lay their eggs in stagnant water and dark bushes, and thus, the disease is more common in these areas.
In terms of person, malaria affects all people. As long as a person is bitten by a mosquito carrying the microorganism, he/she will contract the disease. However, pregnant women and small children are the most affected. In other words, the incubation period of the disease may not develop in other cohorts.
In terms of time, malaria is a common epidemic in the rainy season. Although in some places, the disease is endemic, the population rise of mosquitoes during the rainy season increases the incidence and prevalence of the disease. The incidence of mosquito bites also happens at specific times of the day, at dawn and at dusk. The named factors help determine the best ways to prevent and control the disease.
5. Selection bias refers to the situation whereby the participants of a study are not randomly selected. Consequently, this implies that the researcher selects those participants that suit the topic of study. That is a common type of business, especially in observational studies such as cohort study and case study.
6. Information bias in research is also known as observation bias which occurs mainly during the data collection stage of research. The estimated effect becomes distorted by errors in the measurement tool or in mis-classification of the subject. There are various types of information bias, namely interviewer bias, questionnaire bias, recall bias, diagnostic bias, and exposure suspicion bias. Interviewer bias results from the wrong interpretation of results of a study and can be reduced by using easier ways to interpret data. Questionnaire bias can be effectively minimized by proper scrutiny and screening of the questions to ensure that they are not ambiguous. As a result, this will ensure that the expected information is captured from the study. Recall bias can be avoided by giving the respondents specific clues to enhance memory and recall of information. In case of exposure suspicion bias, the researcher should ensure that the respondents are not exposed to the questionnaires before the study.
7. External validity refers to the ability to generalize results from a study to the target population. Internal validity affects external validity in that lack of the study measuring makes the generalization impossible. Hence, a study can have internal validity, but lack external validity; however, a study without internal validity cannot have external validity.
8. Confounding in research refers to a situation whereby there are factors that are not foreseen and are outside the research; consequently, this affects the results of research. The factors have a significant impact on research in that no measures to control them are possible since they are unexpected.
9. Confounding factors in disease exposure are an important consideration. Most diseases when being studied have distant unrelated factors that may affect the results of such studies. For example, the exposure to a disease may lead to its development in one person but not in another one. If this difference is due to their genetic differences, then genetic difference is the confounding factor.