Complete question:
You want to study the effect of agriculture run-off on the rate of antibiotic-resistant bacteria in ponds. You gather samples from ponds surrounded by high-density livestock areas and from ponds at least ten miles from agriculture activities. You grow the bacteria on plates and test how resistant they are to antibiotics. Based on this experiment, the proximity of the pond to agriculture would be best categorized as what?
- the control group
- the independent variable
- the dependent variable
- the hypothesis
Answer:
2. the independent variable
Explanation:
During an experiment, data from an experimental group is compared with the data from a control group. Both groups are selected from the same pool or population, so they are identical in all aspects except for the independent variables.
The election of a control group is essential in an experiment. Its principal purpose is to allow the discrimination of the results obtained by the treatment in the study, from the results that might be a consequence of other factors. The control group does not receive any treatments. It is used to identify any other factors influencing the results obtained in the study, apart from the modified variables of the treatment.
The <u>experimental group</u> is the one that receives the experimental procedure or treatment. The researcher voluntarily changes the independent variables in the experimental group to observe how they affect the group under study. These variables are kept constant in the control group, not influencing the results, while the experimental group receives the treatment. There can be several experimental groups.
Independent (manipulated) variable: Refers to all the variables in an experiment that provoke a response in another variable. An independent variable is the one that<u> changes</u> or is <u>controlled</u> and <u>modified</u> in the experiment to <u>analyze how another variable responds to it</u>. It changes to analyze its effects on the dependent variable. Usually, the independent variable is represented by the X letter.
Dependent variable: Refers to the variable that depends and reacts to any change in the independent variable. It represents a quantity of something which value depends on how the independent variable is modified. This change might be proportional or inversely proportional to the change in the manipulated variable. It is usually identified by the letter Y.
The hypothesis is a conjecture. The researcher hypothesizes in order to predict what is going on or what is expected to occur. A hypothesis is a claim of how it works a relation between two or more variables. Usually, it is written in the present time.
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The proximity of the pond to agriculture might be considered as an <em>independent variable</em>.
The researcher chooses ponds according to their distance from the crops. In the exposed example, the researcher chose a pond is surrounded by high-density livestock areas and another one at least ten miles away.
The magnitude of run-off might depend on how far the pond is from the crops.
