Ask yourself what you are trying to find out through the research. The difference between quantitative and qualitative research is that they serve two different purposes. Your research question should drive the method you select. Quantitative research methods are used when a researcher is trying to test a relationship between at least two variables, asking the question, "Is this independent variable changing the behavior of this dependent variable?" or "Does this independent variable have a positive or negative relationship with this dependent variable?" Qualitative research methods are used when asking a question that could have multiple answers. Often researchers who are uncertain of what the variables even are will be more prone to use qualitative research.
Ask yourself if combining quantitative and qualitative methods would be valuable. Evaluate the information you will get from conducting a quantitative research method. Will there be follow-up questions that you will likely want to ask to find out more about the reasons for the positive or negative relationship between the independent and dependent variable? If so, consider using a qualitative research approach to uncover underlying reasons for the results of the quantitative portion of your research. This can be applied in reverse. For example, some researchers need to conduct an interview which is a form of qualitative research in order to gain enough feedback to conduct a quantitative research method like a survey.
Recognize threats to validity. For quantitative research, it is important to ensure validity. Two forms of validity that are important to consider are classified as internal and external. Internal validity refers to whether you are able to clearly prove that the independent variable is the cause for the change in the dependent variable. You can control additional variables that you feel might also influence the dependent variables through statistical software such as SPSS. These additional variables, also referred to as control variables, can be factors such as age, gender and educational background. External validity refers to your ability to generalize your conclusions about your sample across a wider group of individuals. A threat to external validity can occur when your sample has specific characteristics that the general population does not contain. It is essential that you state in your research any threats to validity.
Stay neutral. As a researcher, it is imperative that you be cautious not to interject your own thoughts or feelings into the research unless you are conducting a qualitative research method that allows for you to be a part of the method itself.