The survey method is commonly utilized in many types of studies, both in scientific and marketing purposes. One of the specific types of research that make use of the survey method is a panel study, also called as a cohort study.
A panel study, also known as cohort study, is a type of observational and longitudinal study that is utilized in various scientific fields and marketing areas. With a clinical study design, the cohort study is utilized in order to determine risk factors, life histories and other aspects related to a group of people being studied.
What is a Cohort?
The focus of a panel study is a group of people who have a common attribute, experience or characteristic in a particular time period. This group is called the cohort. People that share the fact of being born on the same day, month, year or era may belong to a birth cohort. Other kinds of cohort can be formed depending on the common denominator of the participants.
Types of Cohort Study
In order to create a survey or questionnaire that will satisfy the purpose of the study, one must be able to determine whether the study calls for a retrospective cohort study or a prospective one. The main difference that sets these two types of cohort study apart is the time duration involved.
A. Retrospective Study
A retrospective cohort study includes gathering of past data related to the subject of the study before creating cohort groups of participants. The retrospective cohort study uses archived records as a guide in forming groups of respondents. Thus, a retrospective cohort study is also called as a historical study. For instance, a researcher would like to study the effects of a disease endemic to a province. The first step of his study is to identify and collect data regarding the occurrence of the disease after it struck the location. After analyzing the data, the researcher would form two groups of subjects –one cohort group comprised of people who contracted the disease and another group who did not experience the illness.
B. Prospective Study
The prospective cohort study follows the typical pattern – arranging the cohort groups first before gathering the data required. For example, the Oxford Family Planning Association Study conducted in the United Kingdom included groups of couples who utilize the various methods of contraception.
Over the years, the household panel survey emerged as a sub-type of cohort studies. In a household panel survey, the sampling is performed in a draw lots method in order to gather households to survey. These households are followed by the researchers or interviewers on a yearly basis. Some examples of household panel survey include the British Household Panel Survey and the US Panel Study of Income Dynamics.
Advantages and Disadvantages
Cohort studies are able to gather comprehensive information regarding the exposure of the participants to the object of the study (e.g. a disease, a product, etc) as well as the real experience after the exposure. The research process involved in the cohort studies are easily understood by laymen. On the other hand, cohort studies are significantly expensive to conduct because of the large number of participants needed in most cases. In addition, follow up rates are hard to maintain or increase due to the length of time involved.
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