Scenario
Joe is testing his new drink, “Joe’s Morning Coffee.” Each participant is randomly assigned a coffee amount between 0 and 15 ounces. After drinking, they rate their alertness on a 1–15 scale (higher means more alert). Both variables are normally distributed with mean = 8 and SD = 3. Joe records both measures to analyze the relationship between coffee intake and alertness.
Directions
Use the Correlation slider to set a target r. Each change regenerates a new sample and updates the best-fitting line. Use the Predictor slider to choose a coffee amount (0–15 oz); the yellow guides show the predicted alertness on the blue line, and the prediction is reported below.