Skip to Main Content

We have a new app!

Take the Access library with you wherever you go—easy access to books, videos, images, podcasts, personalized features, and more.

Download the Access App here: iOS and Android. Learn more here!


Evidence-rating schemes consider scientific evidence—also referred to as research—to be the strongest form of evidence. The underlying assumption is that recommendations from higher levels of high-quality evidence will be more likely to represent best practices. While comparatively stronger than nonresearch evidence, the strength of research (scientific) evidence can vary between studies depending upon the methods used and the quality of reporting by the researchers. The EBP team begins its evidence search in the hope of finding the highest level of scientific evidence available on the topic of interest.

This chapter provides:

  • An overview of the various types of research approaches, designs, and methods

  • Guidance on how to appraise the level and quality of research evidence to determine its overall strength

  • Tips and tools for reading and evaluating research evidence

Types of Scientific Research

The goal of research is to produce new knowledge that can be generalized to a wider population by systematically following the scientific method. Research approaches are the general frameworks researchers use to structure a study and collect and analyze data (Polit & Beck, 2017). These fall in three broad categories: quantitative, qualitative, and mixed methods. Researchers use these approaches across the spectrum of research designs (e.g., experimental, quasi-experimental, descriptive), which primarily dictate the research methods used to gather, analyze, interpret, and validate data during the study. The chosen technique will depend on the research question as well as the investigators' background, worldviews (paradigms), and goals (Polit & Beck, 2017).

Quantitative Research

Most scientific disciplines predominantly use a quantitative research approach to examine relationships among variables. This approach aims to establish laws of behavior and phenomena that are generalizable across different settings and contexts. This research approach uses objective and precise collection such as observation, surveys, interviews, documents, audiovisuals, or polls to measure data quantity or amount. Through numerical comparisons and statistical inferences, data analysis allows researchers to describe, predict, test hypotheses, classify features, and construct models and figures to explain what they observe.

Qualitative Research

Qualitative research approaches, rooted in sociology and anthropology, seek to explore the meaning individuals, groups, and cultures attribute to a social or human problem (Creswell & Creswell, 2018). Thus, the researcher studies people and groups in their natural setting and obtains data from an informants' perspective. Using a systematic subjective approach to describe life experiences, qualitative researchers are the primary data collection instrument. By analyzing data, they attempt to make sense of or interpret phenomena in terms of the meanings people bring to them. In contrast to quantitative research, qualitative studies do not seek to provide representative data but rather information saturation.

Mixed-Methods Research

A mixed-methods research approach intentionally incorporates or “mixes” both quantitative and qualitative designs and ...

Pop-up div Successfully Displayed

This div only appears when the trigger link is hovered over. Otherwise it is hidden from view.