Data collection in quantitative research

Scientific measurement is a multi-step process in assigning numbers to variables or elements of a phenomenon. A good outcome from research is guided by scientific intuition and dependent on state-of-the-art instruments and the correct execution of data measurement. Data collection protocols stipulated in randomized controlled trials are the gold standard for any clinical investigations. Practical data collection protocols less stringent than those of randomized controlled trials can be considered as quasi-experimental or pilot studies. Questionnaire surveys are the most popular non-experimental data collection approach in multiple science disciplines. The key to survey studies is the construct of questionnaire items that capture the principal components of the research question. Imaging information systems such as a picture archive and communication system and publicly available clinical and imaging databases can be valuable sources of non-experimental data for answering many research questions. Published literature or unpublished data are used for systematic review studies. Databases from standard authorities or national and international professional bodies are valuable data sources for deep insightful analysis using theoretical and mathematical tools. Scientific knowledge should be generalizable and knowledge claims must be validated with high confidence.