What are the three distinct features of case-control study?

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What are the three distinct features of case-control study?

Science often involves making observations and developing hypotheses. Experiments and further observations are often used to test the hypotheses. A scientific experiment is a carefully organized procedure in which the scientist intervenes in a system to change something, then observes the result of the change.

Q. What factor is changed when testing a hypothesis?

Science chapter 1 test study guide

A factor that does NOT change in an experiment is theconstant
Studying the effect of one thing on another in order to test a hypothesis is a(n)experiment
A factor that is manipulated in an experiment to change the dependent variable is theindependent variable

Q. What is a planned procedure to test a hypothesis called?

Science often involves making observations and developing hypotheses. Experiments and further observations are often used to test the hypotheses. A scientific experiment is a carefully organized procedure in which the scientist intervenes in a system to change something, then observes the result of the change.

Basically, a variable is any factor that can be controlled or changed in an experiment. Scientific experiments have three types of variables: independent, dependent, and controlled.

Q. What tests the effect of one thing on another using controlled conditions?

When possible, scientists test their hypotheses using controlled experiments. A controlled experiment is a scientific test done under controlled conditions, meaning that just one (or a few) factors are changed at a time, while all others are kept constant.

Q. Why is an experiment called a controlled study?

An experiment is called a controlled study because the person conducting the experiment will be able to control the controllable variables or factors. The person conducting the experiment can manipulate the variables other than the independent variables and the number of times the experiment will be done.

Q. What is an example of a positive control?

A positive control group is a control group that is not exposed to the experimental treatment but that is exposed to some other treatment that is known to produce the expected effect. For example, imagine that you wanted to know if some lettuce carried bacteria.

Q. What makes a controlled study?

In a controlled experiment, an independent variable (the cause) is systematically manipulated and the dependent variable (the effect) is measured; any extraneous variables are controlled. The quantitative data can be analysed to see if there is a difference between the experimental group and control group.

Q. What is control in a study?

A scientific control is an experiment or observation designed to minimize the effects of variables other than the independent variable. This increases the reliability of the results, often through a comparison between control measurements and the other measurements.

What are the strengths and weaknesses of case control study?

Advantages and Disadvantages of Case-Control Studies

  • They are efficient for rare diseases or diseases with a long latency period between exposure and disease manifestation.
  • They are less costly and less time-consuming; they are advantageous when exposure data is expensive or hard to obtain.

What are the steps of case control study?

Five steps in conducting a case-control study

  • Define a study population (source of cases and controls)
  • Define and select cases.
  • Define and select controls.
  • Measure exposure.
  • Estimate disease risk associated with exposure.
  • Confounding factors.
  • Matching.
  • Bias.

Q. What are the characteristics of a case-control study?

A major characteristic of case-control studies is that data on potential risk factors are collected retrospectively and as a result may give rise to bias. This is a particular problem associated with case-control studies and therefore needs to be carefully considered during the design and conduct of the study.

Q. What are the steps of cohort study?

Cohort study

  • Identify the study subjects; i.e. the cohort population.
  • Obtain baseline data on the exposure; measure the exposure at the start.
  • Select a sub-classification of the cohort—the unexposed control cohort—to be the comparison group.
  • Follow up; measure the outcomes using records, interviews or examinations.

The case-control method has three distinct features: both exposure and outcome (disease) have occurred before the start of the study. the study proceeds backward from effect to cause; and. it uses a control or comparison group to support or refute an inference.

Q. Which of the following is the best description of a case-control study?

A case-control study is a retrospective study that looks back in time to find the relative risk between a specific exposure (e.g. second hand tobacco smoke) and an outcome (e.g. cancer). A control group of people who do not have the disease or who did not experience the event is used for comparison.

Q. What is the main purpose of a control group in a case-control study?

The purpose of the control group is to determine the relative size of the exposed and unexposed components of the source population.

Q. How do you select cases and controls?

Selection of the Controls

  1. The comparison group (“controls”) should be representative of the source population that produced the cases.
  2. The “controls” must be sampled in a way that is independent of the exposure, meaning that their selection should not be more (or less) likely if they have the exposure of interest.

Q. What are the controls in a case-control 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).

Q. How are controls selected?

In a case-control study, participants are selected for the study based on their outcome status. Thus, some participants have the outcome of interest (referred to as cases), whereas others do not have the outcome of interest (referred to as controls). The investigator then assesses the exposure in both these groups.

Q. How can we prevent selection bias?

Another way researchers try to minimize selection bias is by conducting experimental studies, in which participants are randomly assigned to the study or control groups (i.e. randomized controlled studies or RCTs). However, selection bias can still occur in RCTs.

Q. When would you use a case-control study?

Case–control studies are often used to identify factors that may contribute to a medical condition by comparing subjects who have that condition/disease (the “cases”) with patients who do not have the condition/disease but are otherwise similar (the “controls”).

Why is selection bias a problem?

Selection bias is a distortion in a measure of association (such as a risk ratio) due to a sample selection that does not accurately reflect the target population. This biases the study when the association between a risk factor and a health outcome differs in dropouts compared with study participants.

How do you know if a study has selection bias?

To assess the probable degree of selection bias, authors should include the following information at different stages of the trial or study: – Numbers of participants screened as well as randomised/included. – How intervention/exposure groups compared at baseline.

Q. What are the consequences of selection bias?

It affects the internal validity of an analysis by leading to inaccurate estimation of relationships between variables. It also can affect the external validity of an analysis because the results from a biased sample may not generalize to the population.

Q. Why is it important to remove bias in the selection of things?

It is important for investigators to be mindful of potential biases in order to reduce their likelihood when they are designing a study, because once bias has been introduced, it cannot be removed.

Q. What is meant by selection bias?

(seh-LEK-shun BY-us) An error in choosing the individuals or groups to take part in a study. Ideally, the subjects in a study should be very similar to one another and to the larger population from which they are drawn (for example, all individuals with the same disease or condition).

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