A health professional is investigating whether stress level before a routine practice session can be used to predict the mean stress level before a major figure skating competition. The health professional selected a random sample of 6 figure skaters and measured the stress level before a routine practice session and before a major
competition. Each variable was measured as the change in the interval between heartbeats, or heart rate variability. The health professional wants to estimate the mean
change in the stress level before a major competition for each unit increase in the stress level before a routine practice.