Many journals make this an essential condition for publication. For all the methodological reasons mentioned above and for ethical reasons, the randomized controlled and blinded clinical trial with case number planning is accepted as the gold standard for testing the efficacy and safety of therapies or drugs 4 , e1 , In contrast, noninterventional clinical studies NIS are patient-related observational studies, in which patients are given an individually specified therapy.
NIS include noninterventional therapeutic studies, prognostic studies, observational drug studies, secondary data analyses, case series and single case analyses 13 , The evaluation is often retrospective. Prognostic studies examine the influence of prognostic factors such as tumor stage, functional state, or body mass index on the further course of a disease.
Diagnostic studies are another class of observational studies, in which either the quality of a diagnostic method is compared to an established method ideally a gold standard , or an investigator is compared with one or several other investigators inter-rater comparison or with himself at different time points intra-rater comparison e1.
If an event is very rare such as a rare disease or an individual course of treatment , a single-case study, or a case series, are possibilities. A case series is a study on a larger patient group with a specific disease. The lack of a control group is a disadvantage of case series. For this reason, case series are primarily used for descriptive purposes 3.
The main point of interest in epidemiological studies is to investigate the distribution and historical changes in the frequency of diseases and the causes for these. Analogously to clinical studies, a distinction is made between experimental and observational epidemiological studies 16 , Interventional studies are experimental in character and are further subdivided into field studies sample from an area, such as a large region or a country and group studies sample from a specific group, such as a specific social or ethnic group.
One example was the investigation of the iodine supplementation of cooking salt to prevent cretinism in a region with iodine deficiency. On the other hand, many interventions are unsuitable for randomized intervention studies, for ethical, social or political reasons, as the exposure may be harmful to the subjects Observational epidemiological studies can be further subdivided into cohort studies follow-up studies , case control studies, cross-sectional studies prevalence studies , and ecological studies correlation studies or studies with aggregated data.
In contrast, studies with only descriptive evaluation are restricted to a simple depiction of the frequency incidence and prevalence and distribution of a disease within a population. The objective of the description may also be the regular recording of information monitoring, surveillance.
Registry data are also suited for the description of prevalence and incidence; for example, they are used for national health reports in Germany.
In the simplest case, cohort studies involve the observation of two healthy groups of subjects over time. One group is exposed to a specific substance for example, workers in a chemical factory and the other is not exposed. It is recorded prospectively into the future how often a specific disease such as lung cancer occurs in the two groups figure 2a. The incidence for the occurrence of the disease can be determined for both groups.
Moreover, the relative risk quotient of the incidence rates is a very important statistical parameter which can be calculated in cohort studies.
For rare types of exposure, the general population can be used as controls e6. All evaluations naturally consider the age and gender distributions in the corresponding cohorts. The objective of cohort studies is to record detailed information on the exposure and on confounding factors, such as the duration of employment, the maximum and the cumulated exposure.
One well known cohort study is the British Doctors Study, which prospectively examined the effect of smoking on mortality among British doctors over a period of decades e7. Cohort studies are well suited for detecting causal connections between exposure and the development of disease. On the other hand, cohort studies often demand a great deal of time, organization, and money.
So-called historical cohort studies represent a special case. In this case, all data on exposure and effect illness are already available at the start of the study and are analyzed retrospectively. For example, studies of this sort are used to investigate occupational forms of cancer. They are usually cheaper Graphical depiction of a prospective cohort study simplest case [2a] and a retrospective case control study 2b. In case control studies, cases are compared with controls.
Cases are persons who fall ill from the disease in question. Controls are persons who are not ill, but are otherwise comparable to the cases. A retrospective analysis is performed to establish to what extent persons in the case and control groups were exposed figure 2b.
Possible exposure factors include smoking, nutrition and pollutant load. Care should be taken that the intensity and duration of the exposure is analyzed as carefully and in as detailed a manner as possible.
If it is observed that ill people are more often exposed than healthy people, it may be concluded that there is a link between the illness and the risk factor. In case control studies, the most important statistical parameter is the odds ratio. Case control studies usually require less time and fewer resources than cohort studies The disadvantage of case control studies is that the incidence rate rate of new cases cannot be calculated.
There is also a great risk of bias from the selection of the study population "selection bias" and from faulty recall "recall bias" see too the article "Avoiding Bias in Observational Studies". Table 1 presents an overview of possible types of epidemiological study e8. Table 2 summarizes the advantages and disadvantages of observational studies However, the scientific questions can only be correctly answered if the study is planned and performed at a qualitatively high level e9.
It is very important to consider or even eliminate possible interfering factors or confounders , as otherwise the result cannot be adequately interpreted. Confounders are characteristics which influence the target parameters. Although this influence is not of primary interest, it can interfere with the connection between the target parameter and the factors that are of interest.
The influence of confounders can be minimized or eliminated by standardizing the procedure, stratification 18 , or adjustment The decision as to which study type is suitable to answer a specific primary research question must be based not only on scientific considerations, but also on issues related to resources personnel and finances , hospital capacity, and practicability.
Many epidemiological studies can only be implemented if there is access to registry data. The demands for planning, implementation, and statistical evaluation for observational studies should be just as high for observational studies as for experimental studies.
There are particularly strict requirements, with legally based regulations such as the Medicines Act and Good Clinical Practice , for the planning, implementation, and evaluation of clinical studies. A study protocol must be prepared for both interventional and noninterventional studies 6 , The study protocol must contain information on the conditions, question to be answered objective , the methods of measurement, the implementation, organization, study population, data management, case number planning, the biometric evaluation, and the clinical relevance of the question to be answered Important and justified ethical considerations may restrict studies with optimal scientific and statistical features.
A randomized intervention study under strictly controlled conditions of the effect of exposure to harmful factors such as smoking, radiation, or a fatty diet is not possible and not permissible for ethical reasons. Observational studies are a possible alternative to interventional studies, even though observational studies are less reliable and less easy to control A medical study should always be published in a peer reviewed journal.
Depending on the study type, there are recommendations and checklists for presenting the results. For example, these may include a description of the population, the procedure for missing values and confounders, and information on statistical parameters.
Recommendations and guidelines are available for clinical studies 14 , 20 , e10 , e11 , for diagnostic studies 21 , 22 , e12 , and for epidemiological studies 23 , e Since , the WHO has demanded that studies should be registered in a public registry, such as www.
This demand is supported by the International Committee of Medical Journal Editors ICMJE 24 , which specifies that the registration of the study before inclusion of the first subject is an essential condition for the publication of the study results e When specifying the study type and study design for medical studies, it is essential to collaborate with an experienced biometrician.
The quality and reliability of the study can be decisively improved if all important details are planned together 12 , Conflict of interest statement. The authors declare that there is no conflict of interest in the sense of the International Committee of Medical Journal Editors.
National Center for Biotechnology Information , U. Journal List Dtsch Arztebl Int v. Published online Apr Received Jun 30; Accepted Nov This article has been cited by other articles in PMC. Abstract Background The choice of study type is an important aspect of the design of medical studies. Methods This article describes the structured classification of studies into two types, primary and secondary, as well as a further subclassification of studies of primary type.
Results Three main areas of medical research can be distinguished by study type: Conclusions The study type that can best answer the particular research question at hand must be determined not only on a purely scientific basis, but also in view of the available financial resources, staffing, and practical feasibility organization, medical prerequisites, number of patients, etc.
Classification of study types In principle, medical research is classified into primary and secondary research. Open in a separate window. Basic research Basic medical research otherwise known as experimental research includes animal experiments, cell studies, biochemical, genetic and physiological investigations, and studies on the properties of drugs and materials.
Clinical studies Clinical studies include both interventional or experimental studies and noninterventional or observational studies. Epidemiological studies The main point of interest in epidemiological studies is to investigate the distribution and historical changes in the frequency of diseases and the causes for these.
Table 1 Specially well suited study types for epidemiological investigations taken from [ e8 ]. Study objective Study type Study of rare diseases such as cancers Case control studies Study of rare exposure, such as exposure to industrial chemicals Cohort studies in a population group in which there has been exposure e. Acknowledgments Translated from the original German by Rodney A. Footnotes Conflict of interest statement The authors declare that there is no conflict of interest in the sense of the International Committee of Medical Journal Editors.
Berlin, Heidelberg, New York; Berlin, Heidelberg, New York: As opposed to primary market research, secondary market research is a research technique that does not aim to gather information from scratch but relies on already available information from multiple sources. This research focuses on data or information that was collected by other people and is available for either free or paid use for others. Secondary market research takes into account many different sources for collection of information including government data, office data, newspapers, magazines, the internet, etc.
One of the benefits of doing secondary market research is that it is mostly free and takes a lot less time. Some common examples of qualitative research work include doing face to face interviews, being part of focus groups, etc. Quantitative market research is a kind of market research work that is based on hard facts and statistical data rather than the feelings and opinions of the customers or consumers.
This type of research can prove useful both in terms of primary market research and secondary market research. Some of the common examples of quantitative research include exit surveys, questionnaires, on-site fieldwork and the shopping bag survey.
In fact, another example of quantitative research includes researching of the previously existing financial reports, research papers. This type of research comes out with a wide range of statistics and helps to find out the size of the market as well. The following are the five Primary market research techniques that are most commonly used and applied:.
One of the main ways used to conduct primary market research is through focus groups. This method involves getting a group of people in a room or a place and asking them insightful questions regarding the product, its development, their preferences, and feedback, etc. These types of focus groups can be run or conducted at any location feasible for the company or business.
These days, with advancements in technology and the internet, it is possible to conduct them virtually as well, through the method of video conferencing.
But the main thing here is that the group of people brought together have something in common, for example, either they should belong to the same age group, the same gender and so on. This division of the group or the selection process must depend on the audience targeted or the product of service of the company.
Participants in such focus groups are then compensated by either free coupons, vouchers, gifts or money, etc. Focus groups fall under the qualitative research method and help businesses know a lot about customer or market trends.
Another superb and highly effective way to conduct primary market research is through surveys and questionnaires. One of the most common examples of this research method is the feedback form given to customers at the time of billing at a restaurant. Surveys are also conducted in the form of web questionnaires these days that enable businesses to collect a lot of feedback and then analyze it for further administration. There are two major observation techniques or research methods used in primary market research, and they are observation through interaction and communication with the subject and observation through no interaction and communication with the subject.
This form of research method comes under the quantitative primary research since through it; researchers evaluate or measure the behavior of the respondents or the users in general.
This is more of a personal approach in comparison to surveys and questionnaires, etc. This method of primary research involves scientific tests where hypotheses and variables, etc. This is a quantitative type of market research which may either be controlled out in the field or within controlled environments. In order to understand this form of research, here is an example that you can refer to: A food product company created 3 different food packaging styles and then sold the products to different consumers.
After a limited period of time, it analyzed the sales and came to a conclusion about the preferred packaging style or design. One may think of an in-depth interview to be a quantitative approach to primary market research, but this method, in fact, is a qualitative research that takes into consideration the kinds of choices and preferences a customer base has.
Interviews, unlike focus groups, involve interaction between one moderator and one respondent and several types of modes and methods may be used to conduct them. Interviews may not always be restricted to a set pattern of questions but can also be in the form of a conversation with the target customer base or audience.
This kind of a research method helps to dig further into what the customer wants, and the answers can later be analyzed to come to a conclusion for the final product delivery. Secondary market research is mainly based on collecting information from different sources and then coming to a conclusion. The following are the two main types of Sources of Secondary market research data:.
Internal sources include information that has already been collected by the company and proves useful for future projects, etc. For most businesses, internal sources may prove enough to develop new products and services, and this may not require them to look outside. External sources are those sources that present data that is collected by other businesses or people. External sources can be wide and varied and hence one must follow a controlled approach to assessing them.
E-mail is already registered on the site. Please use the Login form or enter another. You entered an incorrect username or password. Great and in-depth post about marketing! Marketing is so key to being truly successful, and good marketing definitely starts with the proper research. I like your point on effective marketing research leads to encouraging communication.
So much of business is still about networking, word-of-mouth, and effectively communicating out to your audience. Doing the research like you have listed will definitely lead to finding that target audience and discovering new and better ways to communicate with them.
Love this, now I understand the importance and different methods of market research in depth?
The four types of primary market research | [ ] Week 1: Researching Research For Research | Ross Presland-Brown Games Development Says: December 15th, at am [ ] The four types of primary market research | .
Primary research usually costs more and often takes longer to conduct than secondary research, but it gives conclusive results. Secondary research is a type of research that has already been compiled, gathered, organized and published by others.
Primary market research is the most common type of a market research method and is also the most valuable type. It is a method that only answers specific questions and not irrelevant issues. Secondary market r esearch. Secondary research is defined as an analysis and interpretation of primary research. The method of writing secondary research is to collect primary research that is relevant to a writing topic and interpret what the primary research found.
Primary data increases the reliability and authenticity of research and in most of the scientific researches primary data are used. Primary methods of data collection There are different types of primary data and they are used according to the type of study. Primary research is a time-tested method, therefore, one can rely on the results that are obtained from conducting this type of research. Disadvantages of Primary Research One of the major disadvantages of primary research is, it .