Examples of control in the following topics:
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- Ideally, all variables in an experiment will be controlled (accounted for by the control measurements) and none will be uncontrolled.
- Controlled experiments can be performed when it is difficult to exactly control all the conditions in an experiment.
- The simplest types of control are negative and positive controls.
- Positive controls are often used to assess test validity.
- When possible, multiple positive controls may be used.
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- A method that significantly contributes to our success in this matter is the controlling of variables.
- The essence of the method is to ensure that comparisons between the control group and the experimental group are only made for groups or subgroups for which the variable to be controlled has the same statistical distribution.
- Such analyses may be described as "controlling for variable $x$" or "controlling for the variations in $x$".
- Controlling is very important in experimentation to ensure reliable results.
- Discuss how controlling for a variable leads to more reliable visualizations of probability distributions.
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- Numerous studies have been conducted to examine the value of the portacaval shunt procedure, many using randomized controls.
- Of these studies, 63% were conducted without controls, 29% were conducted with non-randomized controls, and 8% were conducted with randomized controls.
- In experimental design, random assignment of participants in experiments or treatment and control groups help to ensure that any differences between and within the groups are not systematic at the outset of the experiment.
- Assign subjects with "heads" to one group, the control group; assign subjects with "tails" to the other group, the experimental group.
- It provides control for all attributes of the members of the samples—in contrast to matching on only one or more variables—and provides the mathematical basis for estimating the likelihood of group equivalence for characteristics one is interested in.
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- Controlling.
- Researchers assign treatments to cases, and they do their best to control any other differences in the groups.
- To control for the effect of water consumption, a doctor may ask all patients to drink a 12 ounce glass of water with the pill.
- Researchers randomize patients into treatment groups to account for variables that cannot be controlled.
- Randomizing patients into the treatment or control group helps even out such differences, and it also prevents accidental bias from entering the study.
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- The Salk polio vaccine field trial incorporated a double blind placebo control methodolgy to determine the effectiveness of the vaccine.
- The treatment groups and control groups should be as similar as possible.
- This design was known as the observed control experiment.
- Thus, a randomized control design was implemented to overcome these apparent deficiencies.
- Demonstrate how controls and treatment groups are used in drug testing.
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- The experimental group was fed saffron (n = 24) whereas the control group was not (n = 8).
- Only 4 of the 24 subjects in the saffron group developed cancer as compared to 6 of the 8 subjects in the control group.
- What method could be used to test whether this difference between the experimental and control groups is statistically significant?
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- An observational study is one in which no variables can be manipulated or controlled by the investigator.
- An observational study draws inferences about the possible effect of a treatment on subjects, where the assignment of subjects into a treated group versus a control group is outside the control of the investigator.
- This is in contrast with experiments, such as randomized controlled trials, where each subject is randomly assigned to a treated group or a control group.
- In a controlled experiment, the investigator would randomly pick a set of communities to be in the treatment group.
- Observational studies are a type of experiments in which the variables are outside the control of the investigator.
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- The Clofibrate Trial was a placebo-controlled study to determine the safety and effectiveness of drugs treating coronary heart disease in men.
- It is a lipid-lowering agent used for controlling the high cholesterol and triacylglyceride level in the blood.
- Placebo-controlled studies are a way of testing a medical therapy in which, in addition to a group of subjects that receives the treatment to be evaluated, a separate control group receives a sham "placebo" treatment which is specifically designed to have no real effect.
- Therefore, it can be necessary to use a psychoactive placebo, a drug that produces physiological effects that encourage the belief in the control groups that they have received an active drug.
- Outline how the use of placebos in controlled experiments leads to more reliable results.
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- H 0 : p control = p treatment (the drug doesn't work)
- H A : p control > p treatment (the drug works)
- H 0 : p control − p treatment = 0 (the drug doesn't work)
- H A : p control − p treatment > 0 (the drug works)
- In the control group, 60 of 742 patients died.
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- Random assignment helps eliminate the differences between the experimental group and the control group.
- When designing controlled experiments, such as testing the effects of a new drug, statisticians often use the experimental design technique of random assignment.
- Random assignment, or random placement, is an experimental technique used to assign subjects either to different treatments or to a control group (no treatment).
- Consider an experiment with one treatment group and one control group.
- If there are differences between the fertilized plant group and the unfertilized "control" group, these differences may be due to the fertilizer.