Qualitative studies focus on subjective information, such as feelings, experiences or opinions: data that cannot be scientifically quantified. Quantitative research is the opposite, shunning subjectivity in favor of objectivity. Quantitative research focuses on statistics and quantifiable information. Learning about different methods used to study a topic quantitatively and qualitatively can help you decide which form of research is better for your study.

Qualitative Research: Participant Observation

Participant observation means that the participant in the research is observed by the researcher, usually in a natural setting. For example, qualitative researchers studying autistic children often immerse themselves in the child's world by spending time in the home playing with the child, eating dinner with the family and interviewing parents about the child's behavior. Disadvantages include the small-scale nature of the study, which means it's difficult to generalize about the entire population. In overt research, the “observer effect” could play a part; participants might act differently because they're being watched.

Qualitative Research: In-Depth Interview

In-depth interviews allow the researcher to collect detailed information about one individual participant. This gives the researcher the option of asking about anything relevant, and also allows greater control over the direction of the conversation than would be possible in a focus group, which is another qualitative research method that examines groups instead of individuals. In-depth interviews are very useful for gathering personal histories and perspectives. Aside from the inability to generalize from in-depth interviews, the “observer effect” can also hide results with this method. For example, participants who are attracted to the interviewer may be inclined to hide negative aspects of their personalities or actions in order to appear more appealing.

Quantitative Research: Questionnaire

Quantitative research commonly uses questionnaires as a method of gaining information from a large number of subjects. To enable generalization and quantification of the results, the questions included are often closed-ended, offering only “yes” or “no” as options for an answer, for example. Or the instrument may provide a choice between a limited number of options. An advantage of this method is that many participants can be studied at once, and the information gathered can be easily collated. A disadvantage is the closed nature of the questions. For example, a question may ask if the test-taker is going to vote for the Republicans or the Democrats in the next election, providing no option for those who wish to vote for an independent.

Quantitative Research: Experimental

Scientific experiments can be used in many ways to produce quantitative results for a study. Experimental studies test the effect of a variable on an outcome. For example, to test the efficiency of a new diabetes drug, participants would be randomly split into two groups. One group would be given the drug, and the other would be given a placebo. A numerical result, such as blood sugar level, would be recorded after the test to determine whether the drug had an effect. Performing experiments can provide strong support for a hypothesis, because of the scientific methodology, but each experiment is limited to testing that one variable. For example, in the hypothetical study described above, the participants could have wildly different diets, which also affects blood sugar levels. Therefore, the results might not really say anything about the drug's effectiveness. However, if all variables are properly controlled -- for example, if the participants were required to eat a set diet during the experiment -- the results can provide compelling support for a hypothesis, or can disprove it altogether.