In a controlled experiment, if a researcher wants to examine the effect of radon exposure to rat longevity, which one would be the independent variable?
a) the rats' longevity.
b) the cage the rats were kept in.
c) radon exposure.
d) neither the radon exposure nor the rats' longevity, because both variables are manipulated.

Primary effectit is the most accurate.

People who utilizes the progression principle will ensure their exercise program increases in frequency, intensity, time, and type. the changes need to happen gradually in order to ensure they make gains in their fitness program. a person who doesn't utilize the progression principle can still gain health benefits from exercising, but will not continue to improve in cardiovascular fitness.