Which of the following is the most accurate definition of a variable?
Any condition that may cause a change in the system being studied
The condition in a system that the scientist can control
Any condition in a system being studied that is intentionally held constant by the scientist
Any condition that may cause a change in the system being studied and can be recorded quantitatively
Why is it generally important for scientists to run controlled experiments?
controlled experiments allow scientists to test how several variables might cause an effect at the same time
controlled experiments are easier and less expensive to setup
controlled experiments allow scientists to ensure that any effects that are measured are a result of the one variable that is being changed
scientists generally don't run controlled experiments
Which of the following could be considered the independent variable(s) that is being studied in this experimental setup? (Select all that apply)
Amount of water
rate of gas production
light intensity
plant length
distance from light source
ambient temperature
Which of the following could be considered the dependent variable(s) that is being studied in this experimental setup? (Select all that apply)
Amount of water
rate of gas production
light intensity
plant length
distance from light source
ambient temperature
Which of the following could be considered the constant variable(s) that is being studied in this experimental setup? (Select all that apply)
Amount of water
rate of gas production
light intensity
plant length
distance from light source
ambient temperature
Suppose a scientist is doing an experiment to determine the effect of an all-organic diet on the occurrence of cancer in rats. Which of the following would be the best control group for this experiment?
Rats fed a standard rat diet (not organic)
Rats fed an all-organic diet
Rats fed an all-organic diet, but half the amount of normal
Rats that are not fed anything
Suppose a scientist is doing an experiment to determine the effect of an all-organic diet on the occurrence of cancer in rats. Which of the following would be the best experimental group for this experiment?
Rats fed a standard rat diet (not organic)
Rats fed an all-organic diet
Rats fed an all-organic diet, but half the amount of normal
Rats that are not fed anything
Why is is necessary for scientists to use control group when implementing most experiments?
control groups serve as a way to practice setting up the experimental group and caring for animals
control groups allow the scientist to tell if the specimens were contaminated from the experimental group
control groups allow the scientist to compare the effects on the experimental group to a similar group that was not exposed to the independent variable
In most experiments a control group isn't necessary because they just need to collect data on the experimental group
Consider the research question, "Does the rate of crickets chirping change with temperature?" Which of the following questions correctly identifies the dependent and independent variable?
Temperature is dependent and rate of chirping is independent
Rate of chirping is dependent and temperature is independent
Both temperature and rate of chirping are independent
Both temperature and rate of chirping are dependent
None of the above
Consider the research question, "Does the nitrate concentration affect the size of leaves on an oak tree?" Which of the following choice(s) correctly identifies the variables that would need to be controlled for the experiment.