Differences Between Qualitative and Quantitative Research

What are qualitative and quantitative research methods^1,2

While conducting research for a study, authors undertake different types of research methods depending on their research question and the study type. These research methods are of two types—qualitative and quantitative.

Qualitative research is the process of collecting, analyzing, and interpreting non-numerical data. This method uses reasoning and focuses on the validity rather than the reliability of the results. The observations of this research are expressed in words and help in understanding individuals’ subjective perception about an event, condition, or subject. This type of research is exploratory and is used to generate hypotheses or theories from data. Qualitative data are non-numerical, in the forms of text, videos, photographs, and audio recordings.

Quantitative research is the process of collecting and analyzing numerical data to describe, predict, and control the variables of interest. The results are expressed in numbers and graphs and help in testing the causal relationships between variables, making predictions, and generalizing results. This research is used for testing a theory and then approving or rejecting it based on the results.

Before starting their research process, researchers should understand the different types of research methods to decide the best method for their study type. Most studies use either the quantitative or qualitative method, but in some cases a mixed methods approach may be more useful.

Differences between qualitative and quantitative research¹

The following table lists a few important differences between qualitative and quantitative research.

Parameter	Qualitative research	Quantitative research
Purpose and design	Explore ideas, formulate hypotheses; more subjective	Test theories and hypotheses, discover causal relationships; measurable and more structured
Data collection method	Semi-structured interviews/surveys with open-ended questions, document study/literature reviews, focus groups, case study research, ethnography	Experiments, controlled observations, questionnaires and surveys with a rating scale or closed-ended questions. The methods can be experimental, quasi-experimental, descriptive, or correlational.
Data analysis	Content analysis (determine presence of certain words/concepts in texts), grounded theory (hypothesis creation by data collection and analysis), thematic analysis (identify important themes/patterns in data and use these to address an issue)	Statistical analysis using applications such as Excel, SPSS, R
Sample size	Small	Large
Example	A company organizing focus groups or one-to-one interviews to understand customers’ (subjective) opinions about a specific product, based on which the company can modify their marketing strategy	Customer satisfaction surveys sent out by companies. Customers are asked to rate their experience on a rating scale of 1 to 5

Data collection methods³

Qualitative research

1. Interviews: This helps understand a respondent’s subjective opinion and experience pertaining to a specific topic or event. Semi-structured interviews, which have open-ended questions (where the respondents can answer more than just “yes” or “no”), are commonly used.
2. Document study/Literature review: Researchers’ review of written materials such as archives, annual reports, research articles, guidelines, policy documents, etc.
3. Focus groups: Usually include a small sample of about 6-8 people and a moderator, to understand the participants’ opinion on a given topic.
4. Ethnography: Data are collected through observations and interviews and then analyzed to understand how society and individuals function.

Quantitative research

1. Controlled observations: These are observations made under standard and systematic conditions rather than casual or incidental conditions.⁴ They are conducted in a closed space where the researcher decides the participants and conditions under which the observations will be carried out.
2. Interviews/surveys: These interviews are structured and restricted to closed-ended questions where the respondents must strictly respond with a “yes” or “no” answer. Alternatively, a rating scale may be provided from which the respondents would need to choose a specific rating.

The quantitative data collection methods can be of the following designs⁵:

• Experimental—examines cause and effect
• Quasi-experimental—examines cause; used when not all variables can be controlled
• Descriptive—examines characteristics of a particular situation or group
• Correlational—examines relationships between two or more variables

Quantitative research vs Qualitative research¹

A few advantages and disadvantages of each research method are listed in the table below.

	Advantages	Disadvantages
Qualitative research	Suggests associations, causes, and effects between parameters   Allows for ambiguities in the data, reflects real-world conditions   Uses a descriptive, narrative style	Large-scale data sets are not included because of time and cost constraints   Validity and reliability may be a challenge because of the subjective nature of the data   Replication by other researchers is difficult for the same contexts/situations   Generalization to a wider context is not possible   Time consuming
Quantitative research	More scientific and rational approach   Tests and validates constructed theories   Statistical analysis software ensures quick analysis of large volumes of data   Based on measured values, so it can be checked or replicated by other researchers	Experiments are conducted in controlled settings instead of natural settings   Participants must give objective answers and the reasons for their selection are not considered   Inadequate knowledge of statistical analysis methods may affect the results and their interpretation   Large sample sizes are needed for more accurate analysis

When to use qualitative, quantitative, or mixed methods

The type of research method to be selected depends on a few important criteria:

• Research question and study type
• Miscellaneous: time, costs, data availability, availability of respondents

You could follow this simple rule of thumb:

Objective: To validate or test a theory or hypothesis => Method: Quantitative research

Objective: To understand a topic/event or identify reasons for observed patterns => Method: Qualitative research

A mixed methods approach draws on the strengths of both quantitative and qualitative research in the same study. This method allows researchers to corroborate their findings, verify if the results observed using both methods are complementary, and explain any unexpected results obtained from one method by the other method.³ However, do note that this method could be more effort- and cost-intensive because of the requirement of more resources. The figure above⁶ shows some basic mixed methods research designs that could be used.

To conclude, both quantitative and qualitative research methods comprise several constituent data collection and analysis methods, any of which could be used depending on the study type. We hope that this article has provided an insight into the differences between qualitative and quantitative research so that you could efficiently decide on the most appropriate method for your study.

References

1. McLeod, S. A. Qualitative vs. quantitative research. Simply Psychology, (July 30, 2019). www.simplypsychology.org/qualitative-quantitative.html.
2. American Medical Association. AMA Manual of Style. Section 19: Study design and statistics
3. Busetto L., Wick W., Gumbinger C. How to use and assess qualitative research methods. Neurological Research and Practice [Accessed October 12, 2022] https://neurolrespract.biomedcentral.com/articles/10.1186/s42466-020-00059-z
4. APA dictionary of psychology [Accessed October 17, 2022] https://dictionary.apa.org/controlled-observation
5. Wilson B., Austria M-J, Casucci T. Understanding quantitative and qualitative approaches. University of Utah Health [Accessed October 15, 2022] https://accelerate.uofuhealth.utah.edu/improvement/understanding-qualitative-and-quantitative-approac
6. Mixed methods research. Community Engagement Program. Harvard Catalyst [Accessed October 17, 2022] https://catalyst.harvard.edu/community-engagement/mmr