The Cholesterol Level data sets give cholesterol levels of heart attack patients. Cholesterol measures are taken 2, 4, and 14 days aft er a patient has suffered a heart attack. Is there a significant difference between day 2 cholesterol measures and day 4 cholesterol measures? Carry out a theory-based test and find a 95% confidence interval for the difference. Use the data set CholesterolLevel_day2-4. Summarize your findings, being sure to include a discussion of statistical significance, estimation (confidence interval), causation, and generalization in your answer. Make sure to confirm that validity conditions are met.