The effectiveness of a new over-the-counter pain reliever is tested by measuring the intensity of pain in patients before and after taking the medication. The researchers want to estimate the reduction of pain intensity. What type of inference procedure is required? Select one: O a. Confidence Interval for Difference in Mean - Matched Pairs O b. Confidence Interval for One Sample Mean O c. Confidence Interval for Difference in Two Sample Means O d. Confidence Interval for Difference in Two Sample Proportions O e. None of these inference procedures apply to this scenario