The animation below highlights the things to consider when choosing a research design.
Choosing the right study design video by Bunmi Malau-Aduli and Faith Alele, used under a CC BY NC ND 4.0 licence
The Research Question
In making a decision about the right study design, the first point of consideration is the research question. The aim of the study and the type of research question being asked influences the type of study design that is most appropriate and ultimately determines the choice.4 For example, if the goal is to profer a new treatment option, a quantitative study such as a randomised controlled trial would be the best option. In contrast, prospective cohort research should be conducted if the question is about “prognosis/natural history/exploration of risk factors.4 On the other hand, if the study is related to harmful events, you will likely use a case-control study. Questions that seek to explore people’s perceptions and experiences will require qualitative inquiry, while questions that seek to provide comprehensive and multiple perspectives can utilise mixed-method design.4
Another major factor to consider is the availability of resources, which include project time and funding, as these can limit one’s options for study design.5 Available timeframe for the execution of a research project would determine participant recruitment and data collection options. For example, you may be interested in conducting a prospective cohort study among women to observe the incidence of breast cancer and potential risk factors such as family history and hormone use. As you know, prospective cohort studies require following up with participants over a time period to obtain the outcome, and in the case of breast cancer, this can take several years. However, suppose you have only six months to conduct your research project due to the time constraint. In that case, you may consider conducting a retrospective cohort study instead, which allows you to utilise existing health records. In addition, costs associated with research designs vary. Randomised controlled trials (RCTs) can be very expensive compared to other study designs. Furthermore, studies requiring only a short duration (such as some studies on infectious diseases) are less expensive than studies of chronic illnesses, which may require long-term observation of subjects for years.5
Data availability and study population
Data availability and easy access to/ recruitment of study participants can influence the choice of research design and research topic/question in different ways. For example, enrolling participants in observational studies is typically simpler than enrolling them on intervention trials. Observation studies require less participation time; therefore, prospective participants are more inclined to be interested in participating. In addition, the characteristics of the study population, such as age, type of illness, or location, can also determine the choice of study design.5 For example, if the study utilises online survey for data collection and is targeted at the older population, only some of whom are active online. It wouldn’t be appropriate to use an online survey as a data collection tool, because this may bias recruitment of participants. Instead, it would be better to conduct interviews or focus groups with the participants.
It is also important to assess possible ethical concerns when making study design choices. Based on the research goals and questions, some types of study designs may raise ethical concerns or may not be feasible to conduct ethically.5 Studies that exploit vulnerable populations or involve exposing people to hazardous materials or processes without adequate protection are unethical. For example, RCTs, which are considered the gold standard in quantitative research and evidence-based medicine, may not be feasible in some cases, and other study designs, like observational studies, may be more appropriate. To emphasise the point about the inappropriateness of using RCTs in some cases, two researchers (Gordon and Pell)6 published findings of their systematic review of randomised controlled trials that examined parachute use to prevent death and major trauma related to gravitational challenge. Unsurprisingly, these researchers stated that they could not find any RCT on the research topic. This is because it is unethical and harmful to randomise participants into a group with a parachute and another group without a parachute to assess the effectiveness of parachutes.6
Let’s explore the concept of ethical considerations further because it is a very important aspect of research. Without ethics clearance, it is usually impossible to conduct research.