A case-control study is designed to help determine if an exposure is associated with an outcome (i.e., disease or condition of interest). In theory, the case-control study can be described simply. First, identify the cases (a group known to have the outcome) and the controls (a group known to be free of the outcome).
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What is a case-control study?
Jul 09, 2021 · Excerpt. A case-control study is a type of observational study commonly used to look at factors associated with diseases or outcomes. The case-control study starts with a group of cases, which are the individuals who have the outcome of interest. The researcher then tries to construct a second group of individuals called the controls, who are similar to the case …
How do you compare cases and controls in a case study?
A case-control study is designed to help determine if an exposure is associated with an outcome (i.e., disease or condition of interest). In theory, the case-control study can be described simply. First, identify the cases (a group known to have the outcome) and the controls (a group known to be free of the outcome).
What is a control study in psychology?
It quantifies the relationship between an exposure (such as eating a food or attending an event) and a disease in a case-control study. The odds ratio is calculated using the number of case -patients who did or did not have exposure to a factor (such as a particular food) and the number of controls who did or did no t have the exposure.
What is the or ratio used for in case control studies?
A case-control study is usually conducted before a cohort or an experimental study to identify the possible etiology of the disease. – It costs relatively less and can be conducted in a shorter time. For a given disease, a case-control study can investigate multiple exposures (when the real exposure is not known).
Are control groups used in case studies?
All studies which contain 'cases' and 'controls' are not case-control studies. One may start with a group of people with a known exposure and a comparison group ('control group') without the exposure and follow them through time to see what outcomes result, but this does not constitute a case-control study.
What is the control group in an experiment?
The control group is composed of participants who do not receive the experimental treatment. When conducting an experiment, these people are randomly assigned to be in this group. They also closely resemble the participants who are in the experimental group or the individuals who receive the treatment.Oct 4, 2020
What are the two types of groups in a controlled experiment?
Control and experimental groups The group that receives the treatment in an experiment (here, the watered pot) is called the experimental group, while the group that does not receive the treatment (here, the dry pot) is called the control group.
What is a control group study called?
Control groups may alternatively be called "baseline groups." In a true experiment, control groups are formed through random assignment of respondents, as in between-subject designs, or from the respondents themselves, as in within-subject designs.Jan 1, 2011
What does a controlled experiment test?
A controlled experiment is a scientific test that is directly manipulated by a scientist, in order to test a single variable at a time. The variable being tested is the independent variable, and is adjusted to see the effects on the system being studied.Apr 28, 2017
How do you find the control group?
The control group receives no treatment. The experimental group receives the treatment of the independent variable. Because the flowers getting no dye do not receive the treatment, it is the control group.
Does a controlled experiment have two groups?
A controlled experiment is simply an experiment in which all factors are held constant except for one: the independent variable. A common type of controlled experiment compares a control group against an experimental group. All variables are identical between the two groups except for the factor being tested.Dec 11, 2019
What is the difference between control and variable group?
What is the difference between a control and a variable group? The only difference between the two groups is that the independent variable is changed in the experimental group. The independent variable is “controlled” or held constant in the control group.Jan 3, 2022
What is the difference between a control group and a control variable?
A control variable isn't the same as a control group. Control variables are held constant or measured throughout a study for both control and experimental groups, while an independent variable varies between control and experimental groups.Mar 1, 2021
What is a control group example?
Example of a Control Group Assume you want to test a new medication for ADHD. One group would receive the new medication and the other group would receive a pill that looks exactly the same as the one that the others received, but it would be a placebo. The group who takes the placebo would be the control group.Feb 22, 2022
Why is it called a control group?
The control group (sometimes called a comparison group) is used in an experiment as a way to ensure that your experiment actually works. It's a way to make sure that the treatment you are giving is causing the experimental results, and not something outside the experiment.Oct 1, 2015
What is another word for control group?
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What are the advantages of case control studies?
Case-control studies have specific advantages compared to other study designs. They are comparatively quick, inexpensive, and easy. They are particularly appropriate for (1) investigating outbreaks, and (2) studying rare diseases or outcomes.
Why is case control retrospective?
By definition, a case-control study is always retrospective because it starts with an outcome then traces back to investigate exposures. When the subjects are enrolled in their respective groups, the outcome of each subject is already known by the investigator. This, and not the fact that the investigator usually makes use ...
What are the factors that determine how controls are to be similar to the cases?
Controls. Controls should be chosen who are similar in many ways to the cases. The factors (e.g., age, sex, time of hospitalisation ) chosen to define how controls are to be similar to the cases are the ‘matching criteria’.
Can odds ratios be used without a confidence interval?
An odds ratio without a confidence interval is not very meaningful. These calculations are usually made with computer programmes (e.g., Epi-Info). Case-control studies cannot provide any information about the incidence or prevalence of a disease because no measurements are made in a population based sample.
Is a case control study a case control study?
All studies which contain ‘cases’ and ‘controls’ are not case-control studies. One may start with a group of people with a known exposure and a comparison group (‘control group’) without the exposure and follow them through time to see what outcomes result, but this does not constitute a case-control study.
What is a control group in science?
Revised on April 19, 2021. In a scientific study, a control group is used to establish a cause-and-effect relationship by isolating the effect of an independent variable. Researchers change the independent variable in the treatment group ...
What does it mean to use a control group?
Then they compare the results of these groups. Using a control group means that any change in the dependent variable can be attributed to the independent variable.
What happens if your control group differs from the treatment group?
If your control group differs from the treatment group in ways that you haven’t accounted for, your results may reflect the interference of confounding variables instead of your independent variable.
How to reduce confounding variables?
There are several methods you can use to decrease the impact of confounding variables on your research: restriction, matching, statistical control and randomization. In restriction, you restrict your sample by only including certain subjects that have the same values of potential confounding variables.
What is quasi-experimental design?
While true experiments rely on random assignment to the treatment or control groups, quasi-experimental design uses some criterion other than randomization to assign people. Often, these assignments are not controlled by researchers, but are pre-existing groups that have received different treatments.
How to test the effectiveness of a pill?
To test its effectiveness, you run an experiment with a treatment and two control groups. The treatment group gets the new pill. Control group 1 gets an identical-looking sugar pill (a placebo) Control group 2 gets a pill already approved to treat high blood pressure. Since the only variable that differs between the three groups is the type ...
What is treatment in research?
The treatment is any independent variable manipulated by the experimenters, and its exact form depends on the type of research being performed. In a medical trial, it might be a new drug or therapy. In public policy studies, it could be a new social policy that some receive and not others.
What is the importance of selecting the appropriate group of controls in a case-control study?
An important principle is that the distribution of exposure should be the same among cases and controls; in other words, both cases and controls should stem from the same source population.
Why are age, sex, and race used to match cases and controls?
Age, sex, and race are often used to match cases and controls because they are typically strong confounders of disease.20Confound ers are variables associated with the risk factor and may potentially be a cause of the outcome.8Table 5lists several advantages and disadvantages with a matching design. Table 5.
What is temporal design in observational studies?
Temporal Design of Observational Studies: Cross-sectional studies are known as prevalence studies and do not have an inherent temporal dimension. These studies evaluate subjects at one point in time, the present time.
Why are observational studies important?
Observational studies are an important category of study designs. To address some investigative questions in plastic surgery, randomized controlled trials are not always indicated or ethical to conduct. Instead, observational studies may be the next best method to address these types of questions. Well-designed observational studies have been shown ...
What is the difference between retrospective and prospective studies?
By contrast, cohort studies can be either retrospective (latin derived prefix, “retro” meaning “back, behind”) or prospective (greek derived prefix, “pro” meaning “before, in front of”). Retrospective studies “look back” in time contrasting with prospective studies, which “look ahead” to examine causal associations.
What is the goal of analytic studies?
The goal of analytic studies is to identify and evaluate causes or risk factors of diseases or health-related events. The differentiating characteristic between observational and experimental study designs is that in the latter, the presence or absence of undergoing an intervention defines the groups.
How are data about exposure to a risk factor collected?
Data about exposure to a risk factor or several risk factors are then collected retrospectively, typically by interview, abstraction from records, or survey.
What is a cross sectional study?
A cross sectional study measures the prevalence of health outcomes or determinants of health, or both, in a population at a point in time or over a short period. Such information can be used to explore aetiology – for example, the relation between cataract and vitamin status has been examined in cross sectional surveys. However, associations must be interpreted with caution. Bias may arise because of selection into or out of the study population. A cross sectional survey of asthma in an occupational group of animal handlers would underestimate risk if the development of respiratory symptoms led people to seek alternative employment and therefore to be excluded from the study. A cross sectional design may also make it difficult to establish what is cause and what is effect. If milk drinking is associated with peptic ulcer, is that because milk causes the disease, or because ulcer sufferers drink milk to relieve their symptoms? Because of these difficulties, cross sectional studies of aetiology are best suited to diseases that produce little disability and to the presymptomatic phases of more serious disorders.
Why do studies using controls from the general population tend to overestimate risk?
Studies using controls from the general population will tend to overestimate risk because of differential recall, whereas studies using patients with other types of cancers as controls will underestimate risk if phenoxy herbicides cause cancers other than soft tissue sarcoma.
Is long term recall of dietary habits reliable?
On the other hand, long term recall of dietary habits is probably less reliable . Sometimes exposure can be established from historical records.
Is it safer to use a range of control diagnoses or a single disease group?
If other patients are to be used as referents, it is safer to adopt a range of control diagnoses rather than a single disease group. In that way, if one of the control diseases happens to be related to a risk factor under study, the resultant bias is not too large.
Is it better to use incident or prevalent cases?
In general it is better to use incident rather than prevalent cases . As pointed out in chapter 2, prevalence is influenced not only by the risk of developing disease but also by factors that determine the duration of illness.
Can exposure be made more comparable?
Measurement of exposure can be made more comparable by using patients with other diseases as controls, especially if subjects are not told the exact focus of the investigation. However, their exposures may be unrepresentative.
What is a controlled trial?
A controlled clinical trial that randomly (by chance) assigns participants to two or more groups. There are various methods to randomize study participants to their groups. Example : Meditation or exercise for preventing acute respiratory infection: a randomized controlled trial .
What is cohort study?
Cohort Study (Prospective Observational Study) A clinical research study in which people who presently have a certain condition or receive a particular treatment are followed over time and compared with another group of people who are not affected by the condition.
What is qualitative research?
Qualitative Studies - Research that derives data from observation, interviews, or verbal interactions and focuses on the meanings and interpretations of the participants. Quantitative Studies - Quantitative research is research that uses numerical analysis.
What is the application of longitudinal studies?
Longitudinal Studies - Studies in which variables relating to an individual or group of individuals are assessed over a period of time.
What are the factors that are associated with disease causation?
Any of several factors may be associated with the potential disease causation or outcome, including predisposing factors, enabling factors, precipitating factors, reinforcing factors, and risk factors. Control Groups - Groups that serve as a standard for comparison in experimental studies.
What is systematic review?
A summary of the clinical literature. A systematic review is a critical assessment and evaluation of all research studies that address a particular clinical issue. The researchers use an organized method of locating, assembling, and evaluating a body of literature on a particular topic using a set of specific criteria.
Is there prejudice in case control studies?
There is no sense of prejudice or subjectivity implied in the assessment of bias under these conditions. Case Control Studies - Studies which start with the identification of persons with a disease of interest and a control (comparison, referent) group without the disease.
Control Groups in Experiments
- Control groups are essential to experimental design. When researchers are interested in the impact of a new treatment, they randomly divide their study participants into at least two groups: 1. The treatment group (also called the experimental group) receives the treatment whose effect the researcher is interested in. 2. The control groupreceives e...
Control Groups in Non-Experimental Research
- Although control groups are more common in experimental research, they can be used in other types of research too. Researchers generally rely on non-experimental control groups in two cases: quasi-experimental or matching design.
Importance of Control Groups
- Control groups help ensure the internal validityof your research. You might see a difference over time in your dependent variable in your treatment group. However, without a control group, it is difficult to know whether the change has arisen from the treatment. It is possible that the change is due to some other variables. If you use a control group that is identical in every other way to t…