First of all we must fully understand what Qualitative and quantitative research methods are. Qualitative research is aimed at discovering how and why people act in certain ways, in their own opinion. So it is often a written descriptive informatory piece that allows psychologists to see the reasons behind emotions and actions. Quantitative research on the other hand is usually an experimental type of research. In quantitative methods participants will often take part in experiments that will provide the participant with a comparable score that allows the research to analyse the data and compare all the participants.
Qualitative research is often in questionnaire (includes interviews) or observation form, with open ended questions that allow the participant to be open with their personal experiences rather than closed questions where it is just a yes or no answer. An example of a study like this is Freud’s study of Little Hans (1909) where open ended interviews and questionnaires were used to gain all the information Freud needed for his case study. However its not the case that all questionnaires and observations are Qualitative. Many questionnaires have sections that contain Likert Scales. These are the questions that say, “on a scale of 1 – 10, how do you agree with….”. An example of a Quantitative study would be that of Loftus and Palmer’s reconstruction of automobile destruction study (1974) where questions were asked about opinion of speed of car, which is answerable on a scale and therefore quantitative even though it is on a questionnaire. These questions allow comparisons and statistical analysis so fit into the Quantitative bracket. Many questionnaire use the duel approach and have questions that are quantitative and qualitative.
Because of these differences there is much argument about the scientific value that a qualitative study actually has. Many believe that there is no testable hypothesis so instead of being scientific it becomes more inquisitive and more of an exploratory test, with it being easy to describe ailments but difficult to explain them, so it has lost its scientific rigor.
This is my personal belief that, yes, qualitative research is needed to help gain a useful insight into the personal beliefs of the participant, but no, its is in no way whatsoever scientific. This is also shown by Johansson, Risberg and Hamberg (2003) who, after their meta-analysis have come to the same conclusion, that qualitative is highly relevant, but quantitative is scientific, with a mixture of both being the ideal study method.