![]() Strengths and weaknesses of different types of research studies However, data from a patient series can help form hypotheses that can be tested in other types of studies. The lack of a comparison group makes it hard to draw conclusions from a patient series. If, however, 2 of the 10 women in the standard treatment group also responded, then the new treatment is no better than the standard. If no women in the comparison group responded to standard treatment, then the 2 women who responded to the new treatment would represent a success of the new treatment. If we had a comparison group of 10 women with breast cancer who got standard treatment, we could compare their outcomes to those of the 10 women on the new treatment. With no comparison group, it’s hard to draw firm conclusions about the effectiveness of a treatment.įor example, if 10 women with breast cancer are given a new treatment, and 2 of them respond, how do we know if the new treatment is better than standard treatment? All the patients are given a certain treatment and the outcomes of these patients are studied. ![]() There is no comparison group in a patient series. Patient seriesĪ patient series is a doctor’s observations of a group of patients who are given a certain treatment. In these cases, researchers must use observational studies. Many behaviors, such as smoking or heavy alcohol drinking, can’t be tested in this way because it isn’t ethical to assign people to a behavior known to be harmful. The researchers would then see which group was more likely to develop breast cancer, those who walked 10 minutes a day or those who walked 2 hours a day. In a randomized controlled trial on exercise and breast cancer risk, half the participants might be randomly assigned to walk 10 minutes a day and the other half to walk 2 hours a day. These studies are called randomized controlled trials because people are randomly assigned (as if by coin toss) to a certain treatment or behavior.įor example, in a randomized trial of a new drug therapy, half the people might be randomly assigned to a new drug and the other half to the standard treatment. In randomized controlled trials (randomized clinical trials), researchers divide people into groups to compare different treatments or other interventions. The researchers compare the 2 groups to see if any exposure (such as alcohol use) was more common in the history of one group compared to the other. Controls are people who do not have the outcome.Cases are people who already have an outcome (such as breast cancer).In a case-control study, researchers identify 2 groups: cases and controls. Researchers compare the different groups (for example, they might compare heavy drinkers, moderate drinkers, light drinkers and non-drinkers) to see which group is more likely to develop an outcome (such as breast cancer). Some people will have a certain exposure (such as alcohol use) and others will not. There are 2 types of observational studies:Ī prospective cohort study follows a large group of people forward in time. They report these activities to researchers. They exercise when they want, eat what they like and take the medicines their doctors prescribe. In observational studies, the people in the study live their daily lives as they choose. The strengths of the conclusions they reach.Though they have the same goal, observational studies and randomized controlled trials differ in: Observational studies ( prospective cohort or case-control).The 2 main types of epidemiology studies are: ![]() The goal of epidemiology studies is to give information that helps support or disprove an idea about a possible link between an exposure (such as alcohol use) and an outcome (such as breast cancer) in people. ![]() Types of Research Studies Epidemiology studiesĮpidemiology is the study of the patterns and causes of disease in people.
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