The only independent variable in this experiment is the amount of nitrogen Sarah uses. All of the other variables are dependent on other factor and processes, but Sarah controls the amount of nitrogen that she uses for each plant.
The day before or the day after.
<span>This is avoidance conditioning. Brenda has been able to successfully link the over-the-counter heartburn medicine to an avoidance of discomfort. By taking the pill, she has received a negative reinforcement due to the removal of the indigestion. The reinforcement will likely lead to Brenda continuing to take the medicine until she habituates to it and does not receive the same benefit(s).</span>