Introduction to Epidemiology

This report provides an introduction to epidemiology, including the definition and aims of the field. It discusses the main features of a cross-sectional survey and provides a description and justification of the study design. The report also compares and contrasts case-control and cohort study designs, and discusses the rationale for design selection. It explores the strengths and limitations of each design. Additionally, the report discusses the design and ethical issues in relation to a randomized controlled trial design and identifies a suitable alternative study design. Overall, the report provides a comprehensive overview of epidemiology and its various study designs.

Introduction to
Epidemiology

Contents
INTRODUCTION.....................................................................................................................................3
Question 2..................................................................................................................................................3
Main features of a cross-sectional survey................................................................................................3
Description and justification of cross-sectional study including case definition and sampling strategy. .3
Data Collection........................................................................................................................................3
Potential sources of bias and procedures to reduce bias...........................................................................4
Question 3a................................................................................................................................................4
Compare and contrast case-control and cohort study designs..................................................................4
Rationale for design selection..................................................................................................................5
Define participant groups and discuss sampling......................................................................................5
Strengths and limitations of selected design............................................................................................5
Question 4a................................................................................................................................................5
Discussion of RCT design.......................................................................................................................5
Design issues in relation to this scenario.................................................................................................6
Ethical issues in relation to this scenario.................................................................................................6
Question 4b................................................................................................................................................6
Identification of a suitable alternative study design.................................................................................6
Rationale for design selection in terms of feasibility, ethics, internal validity etc...................................7
CONCLUSION..........................................................................................................................................7
REFERENCES..........................................................................................................................................8

INTRODUCTION
Epidemiology can be defined as the study of the determinants as well as distribution of
health-related states in specific populations. It is important as it helps in improving the long-term
health of individuals globally (Brouwer and van de Beek, 2017). The primary aims of
epidemiology include preventing and reversing the negative health outcomes. The report
includes a description and justification of the main features of a cross-sectional survey. It also
includes a comparison between case-control and cohort design.
Question 2
Main features of a cross-sectional survey
A cross-sectional survey can be defined as a type of survey that collects data in order to
make inferences about a particular population. In simple words, a cross-sectional survey can be
referred to as an observational study that analyzes data from a population. One of the main
features of a cross-sectional survey is that it can help the researcher in comparing two population
groups at a single time. This means that many different variables can be compared at the same
time. But cross-sectional studies do not provide definite information about the cause-and-effect
relationship between two variables.
Description and justification of cross-sectional study including case definition and sampling
strategy
The case definition is to measure the prevalence of blindness in a defined region.
Samples in a research are used in order to make insightful inferences about a particular
population. There are different types of sampling strategies like systematic sampling, clustered
sampling, simple random sampling and snowball sampling that a researcher can adopt based on
the requirement of the research. The sampling strategy that has been used in this study is simple
random sampling. In this type of sampling strategy, each member of the population has an equal
probability or chance of being selected (Methods of sampling from a population, 2020). Simple
random sampling allows the researcher to calculate the sampling error and reduce overall
selection bias.

Data Collection
Primary data is first-hand information which never used by any research as well as it is
collected by investigator individually related to their topic (Das-Munshi, Ford and et.al., 2020).
There are several methods which researcher use for gatherings primary data and formation such
as observation, survey, customer feedbacks, interview, questionnaire as well as many more. By
using these methods investigator will able to gather information related to their topic in effective
manner without facing difficulties. In addition to this, by using primary method of data collection
information gathered is specific as well as related to research topic which provide assistance in
accomplishing aim and objectives of research in better manner. Along with this, for conducting
research in appropriate manner primary data collection is some suitable as well as by using
questionnaire information will be gathered from distinct responds in effective manner. The type
of data is primary and a questionnaire will be used to collect data from the respondents.
Potential sources of bias and procedures to reduce bias
The potential sources of bias can include recall bias, selection bias, performance bias,
detection bias and attrition bias (Lau, Duggal and Ehrhardt, 2018). In order to reduce selection
bias, adequate sequence generation as well as allocation concealment should be done. In order to
reduce performance bias, the researcher should avoid any unintended interventions. Lastly, for
reducing detection bias, there should be data analyst blinding and use of appropriate statistical
methods.
Question 3a
Compare and contrast case-control and cohort study designs
Case-control study designs are retrospective in nature and clearly define two groups at
the start of the study, one with the outcome and the other without it. This type of studies assess if
there is a significant difference in the rate of exposure to a particular risk factor between the two
population groups. Case-control studies identified the risk factors for cholera by comparing the
patients who had the disease with the ones who did not have the disease (Lilja, Wanhainen and
Mani, 2017). On the other hand, cohort study designs can either be retrospective of prospective
in nature. in retrospective cohort study, both the exposure as well as the outcome have happened
and are conducted on a data that already exists. In case of prospective studies, people are

recruited in the study regardless of their exposure to the disease. In context to this scenario,
prospective case-control study design would be suitable.
Rationale for design selection
The rationale behind selecting case-control study design is that it is efficient for studying
diseases that occur rarely or have a long latency period between the exposure as well as
manifestation of the disease. Apart from this, another reason behind choosing this design is that
it is not very costly and also, do not consume a lot of time. The researcher will be able to
complete the research quickly as this type of study design is beneficial when studying dynamic
populations.
Define participant groups and discuss sampling
Participant groups in a study provide an easy way for the researcher to group together the
study subjects. The participant groups for this scenario would be people who have had cholera
and the ones have not had the disease yet. Simple random sampling will be used wherein the
individuals will be chosen randomly from a large population. This will help in reducing bias and
the sample will represent a large population (Oakes and Kaufman, 2017). Also, the cost as well
as time involved in data collection will be less. Sampling is an important component of a
research and helps in yielding significant results. Therefore, it is important to use the appropriate
sampling method in order to ensure that the results of the study are appropriate as well as
relevant.
Strengths and limitations of selected design
One of the strengths of case-control study design is that it is quick in comparison to other
study designs. Also, they are inexpensive, easy and specifically appropriate for investigating an
outbreak and studying diseases or outcomes that are rare. On the other hand, the limitations of
case-control study design are that they are more prone to selection and recall bias. Also, it is
difficult to establish a causality in this type of study design. Lastly, the information obtained on
exposure is subject to observation bias.

Question 4a
Discussion of RCT design
A randomized controlled trial design refers to a type of trial that randomly assigns
participants in a control or experimental group (Roth and et.al., 2018). The subjects are assigned
to either one of the two groups, the one receiving the intervention which is being tested and
another one receiving an alternative treatment. In the given scenario, it will be possible to
conduct a RCT in order to show the access to emergency obstetric care reduces maternal
mortality. Randomised controlled trial designs are comparative in nature which means that one
treatment is directly comparable to another (Advantages and disadvantages of randomised
control study design, 2020). Apart from this, the confounding factors are minimised because of
the unequal distribution of prognostic factors. Randomised controlled trials have become the
standard that all pharmaceutical companies are expected to meet in order to calculate and prove
the level of efficacy as well as safety of a care service.
Design issues in relation to this scenario
There can be certain problems or issues with the design in this scenario, for example, the
hypothesis set for the study could be unclear. Apart from this, there can be multiple objectives
which can make it difficult for the researcher to obtain appropriate and relevant results. Another
issue related to this scenario can be an inappropriate selection of subject criteria as well as a poor
selection of end points. It is important to address these issues in order to ensure that the quality
of the study is maintained. This is also important because any issues in the design can affect the
overall outcome of the research and therefore, mislead the readers. Poor data collection and
statistical analysis can also be cited as issues in case of the given scenario. There can also be a
case wherein the researcher interprets the collected data incorrectly.
Ethical issues in relation to this scenario
There can be various ethical issues that can be associated with this scenario, for example,
the care that is provided to the expecting mothers is not appropriate (Tysnes and Storstein, 2017).
This can have an impact on the overall health of the mothers as well as the child. Obstetrical care
is usually provided by trained healthcare professionals to pregnant women. Another ethical issue
in relation to this scenario can include an unprofessional emergency care being provided to the
expecting mothers. This can lead to an increase in the maternal mortality rate. The healthcare

service providers might not maintain confidentiality of the patients’ information. Malpractice and
negligence from the side of healthcare service providers can also be cited as one of the major
ethical issues that is relevant to the given scenario.
Question 4b
Identification of a suitable alternative study design
A suitable alternative study design can be longitudinal study, which involves obtaining
repeated observations of the same variables, at short as well as long periods of time. It is also
referred to as a type of observational study. With the help of a longitudinal study, the researcher
will be able to detect any changes in the characteristics of the population that has been targeted.
This is obtained at both individual as well as group level for the target audience. Also, the
longitudinal study design will establish the events in a sequence (Watts and Robson, 2018).
Longitudinal studies can either be retrospective or prospective in nature.
Rationale for design selection in terms of feasibility, ethics, internal validity etc.
The rationale for the selection of longitudinal study design is that they are better to
establish the appropriate sequence of events and identify changes in the target audience overtime.
Not only this, the design also helps in providing useful insights into cause-and-effect
relationships. The study design is feasible because longitudinal studies provide useful insights
that might not be possible through any other way (Webb and Cabada, 2018). Apart from this, the
design is ethical and allows the researcher to conduct the research in an ethical and appropriate
manner. internal validity in research represents the extent to which the results for a target
audience that are observed are truthful and accurate. In terms of longitudinal study design, it is
internally valid as the results that are obtained can be relied upon and are relevant to the target
population.
CONCLUSION
From the above report, it can be concluded that there are different types of study designs
that can be used by the researchers based on the requirement of the study. Cohort study design,
case-control design and cross-sectional surveys are some examples of study design. All of these
designs have their individual benefits as well as limitations.

REFERENCES
Books & Journals
Brouwer, M. C. and van de Beek, D., 2017. Epidemiology, diagnosis, and treatment of brain
abscesses. Current Opinion in Infectious Diseases. 30(1). pp.129-134.
Das-Munshi, J., Ford, T. and et.al., 2020. Practical psychiatric epidemiology. Oxford University
Press.
Lau, B., Duggal, P. and Ehrhardt, S., 2018. Epidemiology at a time for unity. International
journal of epidemiology. 47(5). pp.1366-1371.
Lilja, F., Wanhainen, A. and Mani, K., 2017. Changes in abdominal aortic aneurysm
epidemiology. Journal of cardiovascular surgery. 58(6). pp.848-853.
Oakes, J. M. and Kaufman, J. S. eds., 2017. Methods in social epidemiology. John Wiley &
Sons.
Roth, J. A. and et.al., 2018. Introduction to machine learning in digital healthcare epidemiology.
Infection Control & Hospital Epidemiology. 39(12). pp.1457-1462.
Tysnes, O. B. and Storstein, A., 2017. Epidemiology of Parkinson’s disease. Journal of Neural
Transmission. 124(8). pp.901-905.
Watts, R. A. and Robson, J., 2018. Introduction, epidemiology and classification of vasculitis.
Best Practice & Research Clinical Rheumatology. 32(1). pp.3-20.
Webb, C. M. and Cabada, M. M., 2018. Recent developments in the epidemiology, diagnosis,
and treatment of Fasciola infection. Current opinion in infectious diseases. 31(5). pp.409-
414.
Online
Advantages and disadvantages of randomised control study design. 2020. [Online]. Available
through:< https://derangedphysiology.com/main/cicm-primary-exam/required-reading/
research-methods-and-statistics/Chapter%202.0.2/advantages-and-disadvantages-
randomised-control-study-design >.
Methods of sampling from a population. 2020. [Online]. Available through:<
https://www.healthknowledge.org.uk/public-health-textbook/research-methods/1a-
epidemiology/methods-of-sampling-population >.