Research questions and hypotheses?

When doing proposals or client reports, we often refer to “research questions” and “research hypotheses” (sometimes used interchangeably). What is the difference?

Research Questions do NOT entail specific predictions (magnitude or direction of the outcome variable) and are therefore phrased in question format that could include questions about descriptives, difference or association (or relationship). These assist the researcher to choose the most appropriate statistics techniques. Lets look at each:
1. Research questions that relate to describing variables – summarises or describes data with “descriptive statistics” such as means, standard deviations, percentages, ranges, ratios, etc.
2. Research questions that relate to differences – compares two or more groups on scores of the dependent variable, grouped by the independent variable (predictor or factor) to show if groups are the same on the dependent variable. Tests include t-tests, ANOVA, etc.
3. Research questions that relate to associations – determine whether two or more variables are associated or related to one another, how they covariate, or how they predict each other. Associational tests include correlation, regression, etc. 
Research Hypotheses (singular = hypothesis) are predictive statements  about the relationship between variables. Hypotheses are in a statement format, and NOT in a question format.  Not all studies have hypotheses, such as in the more exploratory types of research perhaps to develop hypotheses to be tested in future research. An hypothesis is a statement of prediction, so it describes in very specific terms what we expect the results of the study will be, and should therefore be specified before the study commences, rather than after we have seen the results.
Without providing an explanation here, note that we have several types of hypotheses:
  1. The null-hypothesis and alternative-hypothesis
  2. Directional (one-tailed hypothesis) and non-directional (two-tailed hypothesis)
  3. Direct (positive) directional hypotheses and Inverse (negative) directional hypotheses
Remember: A hypothesis can be disproven, but not proven to be true.