Determine the variables tested in each of the following experiments. If applicab
ID: 92859 • Letter: D
Question
Determine the variables tested in each of the following experiments. If applicable, determine and identify any positive or negative controls. Submit this exercise to your instructor upon completion.
1. A study is being done to test the effects of habitat space on the size of fish populations. Different sized aquariums are set up with six goldfish in each one. Over a period of six months, the fish are fed the same type and amount of food. The aquariums are equally maintained and cleaned throughout the experiment. The temperature of the water is kept constant. At the end of the experiment the number of surviving fish are surveyed. A. Independent Variable: B. Dependent Variable: C. Controls:
2. To determine if the type of agar affects bacterial growth, a scientist cultures E. coli on four different types of agar. Five petri dishes are set up to collect results: One with nutrient agar and E. coli
One with mannitol-salt agar and E. coli
One with MacConkey agar and E. coli
One with LB agar and E. coli
One with nutrient agar but NO E. coli
A. Independent Variable: B. Dependent Variable:
C. Controls:
Explanation / Answer
An independent variable is the variable that is changed or controlled in a scientific experiment to test the effects on the dependent variable.
A dependent variable is the variable being tested and measured in a scientific experiment.
The dependent variable is 'dependent' on the independent variable. As the experimenter changes the independent variable, the effect on the dependent variableis observed and recorded.
In scientific testing, a control group is a group of individuals or cases that is treated in the same way as the experimental group, but that is not exposed to the experimental treatment or factor. Results from the experimental group and control group can be compared.
In first experiment
Independent variable: Size of the aquariums.
Dependent Variable: No. of the fishes
Control: None
In case of second experiment:
Independent Variable: The type of agar.
Dependent Variable: Amount of E. coli growth.
Controls: The positive controls are the petri dishes that consist of a type of agar and E. coli. The negative control is the petri dish with nutrient agar but NO E. coli
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