In business, firms that both cooperate and compete with other firms are described as engaging in "coopetition." A study published in Industrial Marketing Management (February 2016) examined the level of external tension experienced by managers who engage in coopetition. External tension (measured on a 20-point scale) was recorded for each in a sample of 1,532 managers, all from firms that were engaged in coopetition. The sample mean tension was x̅ = 10.82 and the sample standard deviation was s = 3.04.

a. Conduct a test (using α = .05) to determine if the true mean external tension level of all managers who engage in coopetition differs from 10.5 points.

b. Find a 95% confidence interval for the true mean external tension level of all managers who engage in coopetition.

c. Explain how the confidence interval of part b can be used to infer whether or not the true mean differs from 10.5.

d. The test, part a, yields a "statistically significant" result. Use the confidence interval, part b, and the fact that external tension is measured on a 20-point scale to comment on whether the result is "practically significant."