The study designs in quantitative research are different from the study designs in qualitative research. The following reasons can best describe the difference between quantitative research and qualitative research. Quantitative research involves collection of numerical data, it deduces a relationship between theory and research. Quantitative research uses scientific/empirical approach to solve the problems. To solve the problem under study the researcher formulates a hypothesis. The researcher then decides about the study design to accomplish his research. The study design should outline the sample selection, data collection, data analysis, and data interpretation. On the other hand, qualitative research basically have simple study designs and there is little or no difference between the study design and the instrument of data collection.
Types of study designs in quantitative research
There are many study designs in quantitative research most of them have been tested for their reliability and validity. They are well recognized, structured and well-defined. Quantitative research designs are structured and sequential. Quantitative study designs can be easily differentiated from their method or instrument of data collection. On the other hand, qualitative research designs do not have vivid classification between the two. Many of the qualitative study designs are mere data collection methods. Quantitative study designs are very specific in nature. One of the aim of quantitative research is to provide enough details so the same study can be replicated for the verification purpose.
The study designs in quantitative research can be categorized on the basis of 1) reference period, 2) number of contacts, or 3) nature of investigations. In quantitative studies there are many study designs some of them are as follows:
On the basis of reference period, there can be following quantitative study designs:
Retrospective studies study an event, situation, or a phenomenon as it happened in the past. Retrospective study designs are often criticized for possible risk of biases to avoid this the researchers take sufficient sample size. They also make sure that they avoid all the chances of bias in their study. The researchers look for the data either in the form of print or other medium that is already present or they ask respondents who can recall the situation.
Prospective studies study the prevalence and outcome of a situation, event, or phenomenon in future. Researchers in the field of medical science study the prospects of a disease taking a specific sample. During the study period they study the possible risk and protection factors to understand the disease. In prospected study designs the researcher has to be very cautious the sample size should not diminish during the study otherwise their study will become biased will be less accurate.
Retrospective-prospective studies are long duration studies that study a phenomenon, situation, or event in the past and then apply this information to study its future. These studies study a phenomenon that is already happened in the past and then introduce the intervention to the respondents and study future outcomes. Some types of retrospective-prospective studies are trend studies and before-and-after studies.
To decide whether to use experimental or non-experimental study design depends on the type of research question. Both experimental and non-experimental study designs have their benefits and drawbacks.
Experimental study designs are based on testing a hypothesis. These designs have an independent variable, a dependent variable, and a control group. The researcher controls every external factor that can impact the dependent variable and can introduce bias in the experiment. Such experiments are conducted in a controlled laboratory environment. Such studies are very scientific/empirical and aim at high reliability, accuracy, and validity of the results.
Non-experimental studies are retrospectively conducted the researcher explores the situation that has already happened in the past. The aim of such studies is to know reason for a cause that is already been there. They are the opposite of the experimental studies in which first the intervention is introduced and then the cause is observed as it takes place.
Quasi-experimental studies are semi-experimental studies and they have both the properties of experimental and non-experimental studies. Part of the study is performed under controlled experimentation situation and part of the study is conducted in a non-experimental situation.
Number of contacts means that how many times the audience is approached to study the impact of an intervention or to study a phenomenon or a situation.
Cross sectional studies
Cross sectional studies take a cross section of the population and study a phenomenon, situation, or event under consideration. The aim of these studies is to study the situation in the present, these studies do not aim at studying the change and the factors causing change. Cross sectional studies are simple in design the researcher takes a cross section of the population (or a sample) studies it at one time and find the prevalence of a situation.
Before-and-after studies study the target population before the intervention is introduced to them and once again they study them when the intervention has worked. The aim of these studies is to know what effects a cause. Experimental studies are before-and-after studies as in experimental studies you introduce the intervention, let the intervention work and then study the outcomes. In before-and-after studies the researcher has two contacts with the population and studies the extent of change in the situation.
Longitudinal studies study the pattern of change in a situation, phenomenon, or event. They are conducted over a period of time during this time the researcher contacts the population or the sample at a particular intervals. These intervals may or may not be same but the purpose is to know the pattern of change. Longitudinal studies are very useful in understanding how a change took place.
- “Retrospective VS. Prospective Studies.” Statistical Help. <https://www.statsdirect.com/help/basics/prospective.htm>. Retrieved on 2019/02/04.
- Kumar, R., (2011) Research Methodology: A Step-by-Step Guide for Beginners, Sage Publications: 3rd Ed., New Delhi. Pp- 105-118.