Research Hypotheses

The research hypothesis is central to all research endeavors, whether qualitative or quantitative, exploratory or explanatory. At its most basic, the research hypothesis states what the researcher expects to find – it is the tentative answer to the research question that guides the entire study. Developing testable research hypotheses takes skill, however, along with careful attention to how the proposed research method treats the development and testing of hypotheses.

Before jumping into writing research hypotheses it is crucial to first consider the general research question posed in a study. This seemingly obvious aspect of research can be deceptively difficult to pin down, as researchers often have an unstated sense of what they want to achieve in a study (and excitement about doing so) that makes it challenging to clearly state a research question. Glenn Firebaugh (2008) identified two key criteria for research questions: questions must be researchable and they must be interesting. Researchable implies that a question can be answered through empirical research (that is, something that science can address) and also limited enough that a study could actually hope to answer the question in a reasonable period of time. The requirement that the research question be interesting implies primarily that the question be important in the context of the ongoing scientific discussion of the topic (that is, interesting to other researchers).

Hypotheses in Quantitative Studies
Research hypotheses in quantitative studies take a familiar form: one independent variable, one dependent variable, and a statement about the expected relationship between them. Generally the independent variable is mentioned first followed by language implying causality (terms such as explains, results in) and then the dependent variable; the ordering of the variables should be consistent across all hypotheses in a study so that the reader is not confused about the proposed causal ordering. When both variables are continuous in nature, language describing a positive or negative association between the variables can be used (for example, as education increases, so does income). For hypotheses with categorical variables, a statement about which category of the independent variable is associated with a certain category of the dependent variable can be made (for example, men are more likely to support Republican candidates than women). Continuous variables can also be spoken about it categorical terms (those with higher education are more likely to have high incomes).

Most researchers prefer to present research hypotheses in a directional format, meaning that some statement is made about the expected relationship based on examination of existing theory, past research, general observation, or even an educated guess. It is also appropriate to use the null hypothesis instead, which states simply that no relationship exists between the variables; recall that the null hypothesis forms the basis of all statistical tests of significance. A compromise position is to present a research hypothesis which states a possible direction for the relationship but softens the causal argument by using language such as “tends to” or “in general.”

Hypotheses in Qualitative Studies
Hypotheses in qualitative studies serve a very different purpose than in quantitative studies. Due to the inductive nature of qualitative studies, the generation of hypotheses does not take place at the outset of the study. Instead, hypotheses are only tentatively proposed during an iterative process of data collection and interpretation, and help guide the researcher in asking additional questions and searching for disconfirming evidence.

Qualitative research is guided by central questions and subquestions posed by the researcher at the outset of a qualitative study. These questions usually employ the language of how and what in an effort to allow understanding to emerge from the research, rather than why, which tends to imply that the researcher has already developed a belief about the causal mechanism. In general a qualitative study will have one or two central questions and a series of five to ten subquestions that further develop the central questions. These questions are often asked directly of the study participants (through in-depth interviews, focus groups, etc.) in recognition of the fact that developing an understanding of a particular phenomenon is a collaborative experience between researchers and participants.