quantitative analysis: association, correlation, and causation, political science help

Chapter 5 of the course text discusses three important concepts in quantitative analysis:association,correlation, andcausation. In 250 to 300 words, define the difference between these three terms in scientific research. In your opinion, which is the most valuable concept in research? How difficult do you believe it is to determine each of these terms in quantitative research? Lastly, why is it so difficult to determine causation in research studies?