There are different approaches to research, and different study designs are used to answer different questions. These may reflect fundamental approaches to research within a discipline. Qualitative research is a naturalistic interpretive approach that seeks to describe and explain how and why people act and make decisions. Quantitative research seeks to identify factors or relationships in a sample that can be assumed to be true of the population from which the sample was drawn.

The choice of study design may also be influenced by pragmatic issues such as funding or patient considerations. Regardless of study design, research methods need to ensure that valid and reliable answers are retrieved.

There are many different types of studies. Each study design has advantages and disadvantages and has its own unique potential sources of bias. A study design in itself is not better than another type. It depends on the question being asked.

Descriptive studies are used to describe the frequency or possible determinants of a condition. Cross-sectional studies are a snapshot at a particular time looking at the presence or absence of a disease or symptom or disease and the presence or absence of an exposure. Cohort studies look forward to see if there is a correlation between exposure and an outcome. Case control look backward to see if an outcome was preceded by a common event such as a disease, symptom or exposure to a material. Non-randomised and randomised trials look forward but also compare the effects from a common starting point for two groups. In a non-randomised group, investigators assign participants to a group whereas in a randomised study, participant allocation is by chance. Randomised allocation reduces the likelihood of a systematic variable affecting the outcome.

To assess new therapeutic or pharmacological interventions, randomised controlled trials are commonly regarded as the gold standard particularly because they can measure against a control of current practice. The National Health and Medical Research Council (NHMRC) has developed a pilot programme of additional levels of evidence that matches levels of evidence, types of study design and research questions.

Research in palliative care involve the study of complex interventions such as a new  model of service delivery or the implementation of a new therapy in the community setting across multiple providers. The Medical Research Council (UK) has produced A Framework for development and evaluation of RCTs for Complex Interventions to Improve Health.

This page was created on 25 March 2008 and is due for review in March 2010