Qualitative vs Quantitative Research

The distinction between qualitative and quantitative research is much simpler than the difference between observational and experimental research.  Both qualitative and quantitative methods are aspects of observational research, and they differ in the type of information you observe for your research.  Qualitative and quantitative research have different advantages, and disadvantages, though, so you should be sure to choose the right method for the question you are studying.

The main difference between qualitative and quantitative research is the type of data you analyze.  Qualitative methods include interview research, historical narratives, and text or image analysis.  These methods share a focus on thick data – lots of detail and many different types of information about the cases you study.  Interview or focus group research allows for open-ended questions that let the interview subjects guide what you study.  Archival research may look at the content of hundreds of documents for what they say about political events.

Quantitative research uses numbers.  While interview research asks open-ended questions, survey research will ask multiple choice questions.  Statistical analysis will translate the concepts you are studying into numerical variables that we can do math with, generating tables and graphs we can analyze.  And while qualitative text analysis focuses on the meaning and context of documents, quantitative text analysis involves scraping information of the web (like all the tweets by a person) and analyzing the content with computers (counting words, for example, or the timing of social media posts).  Even images can be analyzed quantitatively, breaking them down into their parts.

We will discuss all of these methods in the last two modules of our course.  For right now, I want you to realize you have many options for how you can study a topic, but these options have advantages and disadvantages.  Qualitative research tends to be good at establishing internal validity, but not external validity.  Quantitative research is the opposite.  Since qualitative research provides a lot of detail on the ideas you are studying and how they relate to each other, it often does a good job at describing causal mechanisms.  But since you can’t study many cases with that level of detail, you often can’t apply the conclusions you draw to many other contexts.  Quantitative research allows you to analyze hundreds or thousands of observations at a time – you can study representative samples and feel like you are accurately representing the universe of cases you want to learn about.  But because you have to make hard choices when you translate your concept to a numerical variable, you often have measurement bias.  And it is hard to include all the alternate explanations in any study, making it hard to establish causality.

Because these types of research have complementary strengths and weaknesses, we often do multi-method research – using both qualitative and quantitative techniques to study a question.  For example, in my dissertation research, I conducted both surveys and interviews of members of parliament.  This is a best practice for real-world research, but for this class, I recommend you focus on one method.  It is okay for that method to have weaknesses, as long as you know what they are.  No research is ever perfect.