Shirley Quach, RRT HBSc Research Interest Group Co-Chair

Quantitative research focuses on numerical, objective measures of data collection to answer a research question. The research objective differs from qualitative research.

In quantitative research, the researcher is interested in measuring data that can be statistically analyzed to explain relationships between an independent and dependent variable. The conclusions from a quantitative study may be used to explain a certain phenomenon that exists between variables of a given population.

There are 4 types of quantitative research approaches:


Researchers will observe, understand and explain real-life scenarios from available data. The variables are uncontrolled, and the researchers collect quantifiable data for data analysis. E.g. observational studies, prospective/ retrospective cohorts, cross sectional studies, longitudinal design. It can answer what, when, where, when and how questions, but not why questions.

Example of a descriptive quantitative study:
Owen, G. D., Stollings, J. L., Rakhit, S., Wang, L., Yu, C., Hosay, M. A., & Anzueto, A. R. (2019).
International Analgesia, Sedation, and Delirium Practices: a prospective cohort study.
Journal of intensive care, 7(1), 25.Study Objectives
The objectives of this study were to characterize trends in pain and sedation strategies over time and across world regions using actual patient care data and to identify aspects of clinical practice associated with occurrence of delirium in critically ill patients.Study Design
Over the course of 1 month, clinical data were collected prospectively every 6 years from 1998 to 2013 on mechanically ventilated patients until discharge, death, or 28 days after admission. Investigators analyzed how analgesia and sedation strategies varied across years and regions, including proportion of patient days receiving analgesics and sedatives, choice of sedatives, and performance of spontaneous awakening trials (SATs). Secondly, they investigated how occurrence of delirium varied by year and region.Study Conclusions
Within the cohorts of mechanically ventilated adults studied, investigators observed substantial differences in sedation strategies between 2010 and 2016. Practices varied widely between regions. Benzodiazepine usage decreased among all regions, though benzodiazepines remained the sedative of choice in Africa, Latin America, and Asia in 2016. Despite increases in the performance of SATs, especially in the US/Canada region, SATs were performed a minority of the time. Occurrence of delirium increased slightly overall possibly due to observation bias and limited delirium monitoring.


The purpose is to explore and understand relationships between variables, but this is still observational in nature. Researchers will have little to no manipulation on the variables. The data collected are observed and will be statistically analyzed to determine whether a relationship exists.

Example of a correlational study:
Khalil, Y., Ibrahim, E., Shabaan, A., Imam, M., & Behairy, A. E. (2012).
Assessment of risk factors responsible for difficult weaning from mechanical ventilation in adults.
Egyptian Journal of Chest Diseases and Tuberculosis, 61(3), 159-166.Study Objectives
The aim of this work was to identify the most important risk factors responsible for difficult weaning from mechanical ventilation in adult patients.Study Design
This study included 31 patients requiring mechanical ventilation with difficult weaning according to Brochard’s classification [14] (Patients who fail initial weaning and require up to three SBT or as long as 7 days from the first SBT to achieve successful weaning).After failure of weaning the patient is reevaluated to detect the risk factors responsible for difficult weaning:

  • Drug history during the period of ICU stay including corticosteroids, sedatives, and aminoglycosides.
  • Cardiovascular system evaluation
  • Neuromuscular evaluation
  • Radiological assessment
  • Thyroid function tests
  • Assessment of some serum electrolytes
  • Blood and urine cultures (if needed) to search for a source of recent infection.
  • Tracheal aspirate culture for aerobic & anaerobic bacteria and fungi.
  • Routine hematological profile (CBC, renal and hepatic functions) after failure of weaning.

Study Conclusions
Attention should be paid for assessment, early detection and management of these risk factors to achieve successful weaning. These factors include: Infections both pulmonary and extra-pulmonary, Cardiovascular dysfunctions, Electrolytes and trace elements disturbances, Psychological problems (anxiety and depression), Inadequate nutrition, Metabolic factors, Endocrinal dysfunctions as hypothyroidism, Drug therapy during the ICU sat as corticosteroids, aminoglycosides and sedatives, Neuromuscular dysfunctions including peripheral neuropathy and critical illness mypoathy acquired during ICU stay.

Prolonged use of invasive devices (urinary and central venous catheters) is usually associated with higher incidence of infection and longer duration of mechanical ventilation. Open surgical tracheostomy may be a contributing factor for weaning failure and higher mortality among the studied cases.


This method may appear experimental, but there is actually minimal intervention from the researchers. Once coming up with a research question, the researchers identify individuals into control groups. The control group is not manipulated by the research team, but they are exposed to the interested variables. The data collected are compared to groups that were not exposed to the variables being investigated.
Eg. pre/post studies.

Example of a Quasi-experimental study
Sousa, A. S., Ferrito, C., & Paiva, J. A. (2019).
Application of a ventilator associated pneumonia prevention guideline and outcomes: A quasi-experimental study.
Intensive and Critical Care Nursing, 51, 50-56.Study Objectives
The aim of the study was to assess whether a customised guideline implementation would improve ventilator-associated pneumonia incidence and associated intensive care outcomes.Study Design
This was a quasi-experimental, before-after study consisting of pre-intervention, intervention and post-intervention periods.A set of eight recommendations was implemented after a guideline adaptation process. Data related to patient characterisation, guideline compliance and health outcomes were analysed (LOS, incidence of VAP, Mortality).Study Conclusions
This study showed that the improvement of health outcomes regarding VAP is possible through the development of an evidence-based guideline, adapted to local conditions, coupled with an implementation process to guarantee its effectiveness.


This is considered to be true experimentation, as these methods aim to understand the cause-effect relationship between variables. The researchers try to control for all the possible variables, except for the independent variable being studied. The independent variable is the only variable that can change during the experiment, identified as the “cause” and the dependent variable (the “effect”) is measured for data analysis.
Eg. randomized controlled trial, crossover designs.

Example of a experimental study
Nebulized Versus IV Amikacin as Adjunctive Antibiotic for Hospital and Ventilator-Acquired Pneumonia Post cardiac Surgeries: A Randomized Controlled Trial

Study Objectives
This study evaluates the efficacy and nephrotoxicity of nebulized versus IV amikacin in post cardiothoracic surgical patients with nosocomial pneumonia caused by multidrug-resistant Gram- negative bacilli.

Study Design
Prospective, randomized, controlled study on surgical patients divided into two groups.The first group was administered IV amikacin 20 mg/kg once daily. The second group was prescribed amikacin nebulizer 400 mg twice daily. Both groups were co-administered IV piperacillin/tazobactam empirically. Recruited patients were diagnosed by either hospital-acquired pneumonia or ventilator-associated pneumonia. Clinical cure in both groups assessed on day 7 of treatment was the primary outcome. Efficacy was additionally evaluated through assessing the length of hospital stay, ICU stay, days on amikacin, days on mechanical ventilator, mechanical ventilator-free days, days to reach clinical cure, and mortality rate.

Study Conclusions
Nebulized amikacin showed better clinical cure rates, less ICU stay, and fewer days to reach complete recovery compared to IV amikacin for surgical patients with nosocomial pneumonia. It is also a less nephrotoxic option associated with less deterioration in kidney function.

Given the quantifiable data that is collected in a quantitative study, the data is statistically analyzed to provide numerical outcomes.

This information was derived from the following resources:

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