A control group is essential in clinical trials (except for crossover trials where participants act as their own controls). 2 Trial participants are randomly allocated to an experimental treatment, such as a new drug, or to the control group.
Full Answer
What is the control group in a research study?
The control group consists of participants who do not receive the experimental treatment being studied. Instead, they get a placebo (a fake treatment; for example, a sugar pill); a standard, nonexperimental treatment (such as vitamin C, in the zinc study); or no treatment at all, depending on the situation.
What are the treatment and control groups in a comparative experiment?
Treatment and control groups. In comparative experiments, members of the complementary group, the control group, receive either no treatment or a standard treatment. A placebo control group can be used to support a double-blind study, where a portion of patients are given a placebo medication (typically, sugar pill ),...
What is the difference between treatment and control group?
Treatment and control groups. In the design of experiments, treatments are applied to experimental units in the treatment group (s). In comparative experiments, members of the complementary group, the control group, receive either no treatment or a standard treatment. A placebo control group can be used to support a double-blind...
What are treatment and control groups in a double blind study?
Treatment and control groups. A placebo control group can be used to support a double-blind study, where a portion of patients are given a placebo medication (typically, sugar pill ), in order to observe the patients are taking their medications in the manner as proscribed, with no major procedural differences between the treatment group(s)...
What kind of studies have control groups?
Almost all experimental studies are designed to include a control group and one or more experimental groups. In most cases, participants are randomly assigned to either a control group or an experimental group.
What is a study called with a control group?
A true experiment (a.k.a. a controlled experiment) always includes at least one control group that doesn't receive the experimental treatment. However, some experiments use a within-subjects design to test treatments without a control group.
Are control groups still used in medical research?
The use of multiple control groups is becoming more common in clinical trials. Several doses of test drug and several doses of an active control, with or without a placebo are used. This control group is useful for actively comparing the potency of two drugs.
Which method of research involves a treatment group?
experimental researchIn experimental research, some subjects are administered one or more experimental stimulus called a treatment (the treatment group ) while other subjects are not given such a stimulus (the control group ).
Why Some studies include both a control group and a placebo treatment?
Both placebos and controls are used in research studies to prevent the placebo effect, or the real or apparent improvement in a patient's condition due to wishful thinking by the investigator or the patient.
What is control group in clinical trials?
Listen to pronunciation. (kun-TROLE groop) In a clinical trial, the group that does not receive the new treatment being studied. This group is compared to the group that receives the new treatment, to see if the new treatment works.
Why studies should have a control group?
Having more than one control group increases the power of a study and reduces the bias. Increase in power is achieved because of greater comparability as more information is available regarding potential differences in response between cases and controls.
Why control group is important for scientific study?
The control group consists of elements that present exactly the same characteristics of the experimental group, except for the variable applied to the latter. This group of scientific control enables the experimental study of one variable at a time, and it is an essential part of the scientific method.
What is a control treatment examples?
The experimental group is given the experimental treatment and the control group is given either a standard treatment or nothing. For example, let's say you wanted to know if Gatorade increased athletic performance. Your experimental group would be given the Gatorade and your control group would be given regular water.
Which type of research involves studying the same group of individuals over time?
Longitudinal design is used to discover relationships between variables that are not related to various background variables. This observational research technique involves studying the same group of individuals over an extended period.
Do quasi experiments have control groups?
"Quasi-experimental research is similar to experimental research in that there is manipulation of an independent variable. It differs from experimental research because either there is no control group, no random selection, no random assignment, and/or no active manipulation."
What are the 4 types of experimental design?
While this type of research falls under the broad umbrella of experimentation, there are some nuances in different research design. Four major design types with relevance to user research are experimental, quasi-experimental, correlational and single subject.
What is treatment in comparative studies?
In comparative experiments, members of a control group receive a standard treatment, a placebo, or no treatment at all. There may be more than one treatment group, more than one control group, or both.
What is a placebo control group?
A placebo control group can be used to support a double-blind study, in which some subjects are given an ineffective treatment (in medical studies typically a sugar pill) to minimize differences in the experiences of subjects in the different groups; this is done in a way that ensures no participant in the experiment (subject or experimenter) knows to which group each subject belongs. In such cases, a third, non-treatment control group can be used to measure the placebo effect directly, as the difference between the responses of placebo subjects and untreated subjects, perhaps paired by age group or other factors (such as being twins).
Is it statistically efficient to randomly assign twins?
In studies of twins involving just one treatment group and a control group, it is statistically efficient to do this random assignment separately for each pair of twins, so that one is in the treatment group and one in the control group.
Can a third control group be used to measure the placebo effect?
In such cases, a third, non-treatment control group can be used to measure the placebo effect directly, as the difference between the responses of placebo subjects and untreated subjects, perhaps paired by age group or other factors (such as being twins).
Why is it important to compare treatment and control groups?
The comparability of the treatment and control groups at randomization is also important because it is the first stage in our investigation of a set of methodological problems that could result in biased estimates of channeling's impact. Differences between treatment and control groups in the types of individuals who fail to respond to interviews could result in noncomparable groups in the sample being analyzed, even if the full samples were comparable. Differences in the way baseline data were collected for treatments and controls could lead to differential measurement error, which could cause regression estimates of program impacts to -be biased. In order to assess these other potential sources of bias, it is important to first determine whether the two groups were comparable before the baseline interview.
How many statistically significant differences are there between treatments and controls?
Out of over 250 comparisons at the five basic sites, we find 15 statistically significant differences between treatments and controls. (at the 90 percent or greater confidence level). This is substantially less than the 25 that might be expected to occur simply by chance. As shown in Table 4, the significant differences were more prevalent in Kentucky than in other sites, but tended to be scattered rather than concentrated in specific variables. Thus, there is no indication of systematic tampering with the random assignment process.
What are the factors that lead to differences in the mean values of the pre-application characteristics of the treatment and control groups?
Only two factors can lead to differences in the true mean values of the pre-application characteristics of the treatment and control groups: deviation from the randomization procedures and normal sampling variability. Deviations from the carefully developed randomization procedures could be either deliberate (e.g., site staff purposely misrecording as treatments some applicants who are randomly assigned to the control group, but who have especially pressing needs for assistance) or accidental (e.g., misrecording of a sample member's status). The dedication and professionalism of this site staff and the safeguards built into the assignment procedure make either occurrence very unlikely. Site staff were extremely cooperative in faithfully executing the procedures. Sampling variability, on the other hand, is the difference between the two groups that occurs simply by chance. For the sample sizes available at the model level, such differences between the two groups should be very small, and statistically insignificant.
Why was the screening instrument used in the Channeling project?
The screening instrument was designed for a short telephone interview, to be administered in a uniform manner by each of the 10 demonstration projects. The telephone screening process was intended to reduce the cost of determining appropriateness for channeling compared to using a comprehensive in-person assessment for that purpose. Channeling project staff who conducted the screening interviews were in a separate administrative unit from assessment and case management staff. This was required chiefly to preserve the integrity of the experimental design--the potential for influencing the behavior of persons assigned to the control groups through contact with channeling staff was minimized by this administrative separation.
What is a screening instrument for nursing home placement?
The screening instrument was developed to identify those elderly individuals who were at high risk of nursing home placement ( those who in the absence of channeling would be in an institution). A set of objective criteria were established that were felt would distinguish such individuals. Data collected from the screen were used to establish whether a given applicant satisfied these criteria and should therefore be classified as eligible. The criteria incorporated the following dimensions: severe functional impairment; expected unmet need in two service categories (e.g., meal preparation, housework, administration of medication or medical treatment, etc.) for six months or more, or expected lack of sufficient help from family and friends in the coming months; residence in the community or, if institutionalized, certified as likely to be discharged into a noninstitutional setting within three months; residence within the project's geographical boundaries; age; and (for financial control sites only) Medicare Part A eligibility. 1
Why is treatment/control difference statistically tested?
However, because of the relatively small number of observations at each site, most of the analysis of channeling will be based on treatment/control differences at the model level, to ensure a high level of precision (i.e., the ability to distinguish between fairly small impacts of channeling and differences between treatment and control groups arising simply by chance).
How are treatments different from controls?
Demographics and living arrangements show no significant differences between treatments and controls for the financial control model. Slightly more treatments than controls are male; slightly more controls than treatments are black. The proportion of treatments with income in excess of 1,000 dollars per month was significantly lower for treatments than controls (5.7 versus 7.3 percent, respectively); however, the difference is not large in absolute terms and the average incomes of the two groups do not differ significantly. Just over 2 percent of both treatments and controls lived in long term care institutions at the time the screen.
What is a randomized controlled trial?
In clinical research, randomized controlled trials (RCTs) are the best way to study the safety and efficacy of new treatments. RCTs are used to answer patient-related questions and are required by governmental regulatory bodies as the basis for approval decisions. Methods.
Why are RCTs used in clinical research?
In clinical research RCTs are used to answer patient-related questions, and in the development of new drugs they form the basis for regulatory authorities’ decisions on approval. Alongside meta-analyses, high-quality RCTs with a low risk of systematic error (bias) provide the highest level of evidence (1, 2).
How was the Alife study randomized?
They were randomized taking account of the prognostic factors of age (<36 years or ≥ 36 years) and number of miscarriages (2 or ≥3), and because the study was multicentric they were stratified by study center. If patients were allocated to treatment groups by conscious or unconscious selection for prognosis-related characteristics, rather than randomly, this could lead to biased treatment comparison and distorted results (selection bias).
What is the purpose of the Alife trial?
The ALIFE trial is a three-armed parallel group study to establish whether the combination treatment or the monotherapy improve the live birth rate compared with placebo. The use of placebos in clinical trials is ethically justified provided that no standard treatment is available. If comparison with placebo is indispensable for methodological reasons, it can be justified as long as patients will not be harmed 18). That is the case, for example, if the study is of only short duration or if the severity of disease permits postponement or interruption of treatment.
What is the quality of an RCT?
The quality of an RCT depends on an appropriate study question and study design, the prevention of systematic errors, and the use of proper analytical techniques. All of these aspects must be attended to in the planning, conductance, analysis, and reporting of RCTs. RCTs must also meet ethical and legal requirements.
What is clinical research?
Clinical research lays the groundwork for progress in medicine and is an indispensable prerequisite for evidence-based medicine. Randomized controlled clinical trials (RCTs) are the gold standard for ascertaining the efficacy and safety of a treatment. RCTs can demonstrate the superiority of a new treatment over an existing standard treatment or a placebo. In clinical research RCTs are used to answer patient-related questions, and in the development of new drugs they form the basis for regulatory authorities’ decisions on approval. Alongside meta-analyses, high-quality RCTs with a low risk of systematic error (bias) provide the highest level of evidence (1, 2).
What is the primary endpoint of the study?
This is a parameter measured or observed that is recorded at a defined time and can be assumed to reflect the effect of a treatment. The endpoint may be clinical, e.g., the live birth rate in the ALIFE study.
What is a case control study?
A case-control study is an observational study in which a group of individuals with disease or condition under investigation (cases) are compared with a group of individuals without that disease (controls). A retrospective cohort study is an observational study in which groups of people are identified and categorized (exposed and non-exposed) based on exposure and followed for a period in the past. Randomized controlled trials (RCTs) and prospective cohort studies are other study designs that include a control group. Due to the random allocation of subjects to treatment or control groups in RCTs, the choice of control group is not at the discretion of the investigator. There is plenty of available literature to inform the control selection process. 3–9The sources from which controls can be selected is a critical issue because each group offers specific advantages and disadvantages that must be carefully considered in order to closely match the treatment group. A vast diversity of sources from which controls can be used include cancer registries, hospital admission rosters, friends and neighbors of cases, or through random-digit-dialed phone calls. Controls in plastic surgery are incorporated either as concurrent or as historic controls. A concurrent control is a subject enrolled simultaneously with the treatment group from the same source population and followed for the same study period, whereas a historical control is a subject treated in the past with the standard form of care whose outcomes are used to compare with patients receiving the treatment under investigation.
How many articles were there in the case control study?
327 articles were obtained from our search using key words ‘case control studies’ and ‘retrospective cohort studies.’ Among these studies, 121 articles were studies conducted in humans. All these studies based on the study design required a control group, yet only 63 studies (52%) had a comparative control group. Of these studies, we found biases regarding the choice of controls, including selection bias, misclassification bias, and chronology bias.
What is historical control?
Distinct from concurrent controls are historic controls, occasionally employed in plastic surgery research (2/63 studies), in which a set of subjects outside the study population who were treated in the past. Use of historical control tends to overestimate the effect of the more current treatment. Differences in diagnostic methodology and outcome assessment methodology used for the historic and intervention groups may result in bias.19Chronology bias occurs when historical controls are used. It is the effect of different time and place between the two comparative groups, which can confound the results.13The improvement in technology and expertise over time will tend to favor the more current treatment. Therefore, historical control use should be restricted to those a study in which enrollment of concurrent controls is not possible. For example, Pannucci et al. examined the effect of post-operative enoxaparin (chemoprophylactic agent) to prevent venous thromboembolism in high-risk plastic surgery patients operated in 2009 by comparing it with a historical control group comprised of patients operated in 2006–2008.20The controls did not receive chemoprophylaxis after surgery because venous thromboembolism was not identified as a major patient safety issue before 2008. With similar eligibility criteria for historical controls as that of intervention patients, the authors ensured comparability and thus validity of the study.
What is no treatment control?
No treatment control, in which a control group is enrolled and observed without any intervention done , was another type of control that was used in plastic surgery (9/61 studies). Because the control group does not undergo any treatment, the outcomes observed in the intervention group can be attributed to the treatment alone, thereby establishing the effectiveness of the treatment. Case-control studies mainly employed this type of control. Such a control can be used only when not providing treatment does not deprive the control group of any benefits that would have been otherwise possible. For example, Caviggioli et al. compared the outcomes of fat tissue grafting in patients suffering from post-mastectomy pain syndrome with patients who did not receive fat grafting after mastectomy but suffered from pain.15This control group established the fat grafting procedure to be a safe, noninvasive, and effective treatment of post-mastectomy pain.
Why do we need more than one control group?
Having more than one control group increases the power of a study and reduces the bias. Increase in power is achieved because of greater comparability as more information is available regarding potential differences in response between cases and controls. This is useful especially in a retrospective study of a rare disease with small number of available cases. However, the increase in power will not be observed after a case to control ratio of 1:4 because this ratio achieves maximum power. 16Enrollment of two or more types of controls allows the researchers to reduce any possible bias due to the choice of a single control group.9For example, in a study of pelvic cancer defects reconstruction, the authors compared the outcomes of vertical rectus abdominis flap (VRAM) reconstruction performed with six technical modification groups.17Fascia sparing, component separation, mesh reinforcement, deepithelized skin paddle, extended VRAM flap and omental flap were the techniques used. Patients in each group served as a control to other groups. Use of more than one control group helped to establish the effectiveness of total VRAM flap deepithelization technique in minimizing donor and recipient-site complications.
When was the first control group used?
The first use of a distinct control group in a clinical study can be traced back to 1926 when Janet E. Lane-Claypon, an English physician, investigated the causation, prevalence and treatment of breast cancer.1In this initial case-control study, cases were women with a history of breast cancer and controls were women without the disease but who were otherwise similar. They found significant associations between the risk of breast cancer and age at menopause, age at pregnancy, number of children and lactation. The introduction of randomization to clinical trials by Bradford Hill, an English epidemiologist in the 1950s led researchers to adopt the idea of a randomized control group for appropriate evaluation of a new intervention.2A control group is comprised of people similar to the test group in all aspects that affect the outcome except for the treatment/intervention of interest. Controls are selected on the basis of comparability to the target population or the population at risk. This group is essential to demonstrate that a treatment or intervention is superior, less costly, or associated with fewer complications compared to the standard practice. Besides helping in the assessment of safety and efficacy, a control group discriminates outcomes caused by the treatment or intervention of interest from those caused by other factors, such as natural course of disease, patient or observer expectations, or other treatments.
When did we perform a literature search in plastic surgery?
We performed a literature search in Plastic and Reconstructive Surgery(PRS) from January 1, 2010 through December 31, 2011 for studies in which controls were needed. The number of studies using a control group, control selection criteria and the characteristics of the control populations were evaluated.
What are the results of a randomized clinical trial?
Figure 1. Results of a randomized clinical trial (RCT) comparing mortality between an investigational treatment and three hypothetical control groups are shown. In comparison to control group 1, mortality in the investigational group is lower. In comparison to control group 3, mortality in the investigational group is higher. In comparison to control group 2, mortality in the investigational group is similar. Thus, depending on the selection and outcomes of the control group, the same investigational treatment would be viewed as beneficial vs. Control 1, harmful vs. Control 3, or neither vs. Control 2.
What are the advantages of randomized controlled trials?
The advantage of RCTs is largely derived from the increased likelihood that measured and unmeasured sources of confounding and selection bias are equally distributed between treatment groups under evaluation ( 1 ). RCTs are, by definition, comparative studies that evaluate differences in experience between two or more groups ( 1 ). Although the interpretation of RCTs usually focuses on the design of an investigational treatment group (s), an equally important issue is the design and outcomes of those randomized to the control group ( 2 – 4 ). Understanding the strengths and weaknesses of the control group used in an RCT is essential, because comparisons of outcomes between the investigational and control groups form the basis of inferences regarding the safety and efficacy of the investigational treatment (s) ( Figure 1 ). Recent controversies have drawn attention to the experience of control participants in clinical trials ( 5 ). For its 2007 International Conference, the American Thoracic Society (ATS) sponsored a symposium on the selection of controls in clinical trials. In this issue of PATS, a number of the speakers from this symposium have provided an overview of methodologic considerations that need to be addressed, and at times balanced, when selecting control groups for clinical trials. In this introduction, we provide a brief historical perspective and a summary of the discussions presented at this ATS-sponsored symposium. Three of the presenters at the symposium (Drs. M. Castro, M.D., M.P.H., T. Thompson, M.D., and R. Sutherland, M.D., M.S.) have written individual manuscripts based on their presentations to provide greater detail and these are included as part of this issue of PATS.
Why are sham procedures used in clinical trials?
Sham procedures for control subjects are used infrequently in clinical trials, but are of particular interest given the recent focus of invasive therapies for emphysema (e.g., endobronchial valves) and asthma (e.g., bronchial thermoplasty) ( 11, 12 ). Dr. Sutherland discussed the history and use of these devices in pulmonary medicine and outlined the need for such interventions because of the history of strong placebo effects associated with invasive procedures ( see article by Sutherland in this issue) ( 13 ). These include a number of widely adopted procedures that were later found to be ineffective when compared with control arms that included a sham procedure ( 14, 15 ). In studies evaluating devices, sham procedures for the control group are desirable because they provide advantages of masking participants (and possibly researchers) to treatment allocation, including minimizing biases resulting from the measurement of some outcomes (e.g., patient-reported symptoms, outcomes requiring researcher judgment) and/or motivation of study participants and researchers to remain adherent to the study protocol. Of course, the use of a sham control group should consider the overall risk of the sham procedure as well.
What are the inferences derived from RCTs?
Inferences derived from RCTs provide the highest level of evidence from clinical research, and depend as much on the design of the control group as the intervention under investigation. As highlighted above, the control group may be assigned to a placebo, best-available therapy, usual- or protocol-driven care, or sham procedure. The governing principles in designing the appropriate control group for RCTs include minimizing the risk to participants, understanding the relationship between the control treatment and clinical practice, and assuring that the control group will provide the appropriate comparison to answer the primary study question.
What is the goal of a research study?
In a research study, the goal is to advance medical science for society and the risks need to be balanced with the knowledge to be gained from the study.
What is the ATS conference?
For its 2007 International Conference, the American Thoracic Society (ATS) sponsored a scientific symposium in which the strengths and limitations of different types of control groups in clinical trials of pharmacotherapy, procedures, devices, and behavioral interventions were discussed.
Is masking of treatment assignment difficult?
In addition, masking of treatment assignment when control groups are used in behavioral studies can be difficult. Furthermore, it is often difficult to develop an “inactive” behavioral control arm that is credible and equally preferable to patients.
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…