Final answer:
Correlated variables change together, but cause and effect variables show direct changes. Results need to be statistically significant to claim a difference caused by the treatment.
Step-by-step explanation:
Two variables that are only identified to have a relationship are correlated and change together, but there is no evidence that one variable is causing a change in the other. On the other hand, two variables that are found to have a cause and effect relationship show that changes in one variable directly result in changes in the other variable.
Results in an experiment need to be statistically significant before making any kind of claim that there is a difference caused by the treatment. Statistical significance means that the observed difference between the treatment groups is not likely to have occurred by chance alone. It provides evidence that the treatment has a real effect on the outcome variable.