2. We would like to estimate the true mean height of all National Hockey League players. A random sample of 16 NHL players is selected and their average height is calculated to be 186.2 cm. Heights of NHL players are known to follow a normal distribution with standard deviation 6.3 cm. (a) Calculate a 95% confidence interval for the true mean height of all NHL players. (b) Provide an interpretation of the interval in (a). (c) Calculate an 88% confidence interval for the true mean height of all NHL players. (d) What happens to the length of the confidence interval when the confidence level decreases? (Does it increase or decrease? )