A random sample of 55 airline pilots had an average yearly income of $99,000 with a standard deviation of $15,000. If we want to determine a 95% confidence interval for the average yearly income, what...

A random sample of 55 airline pilots had an average yearly income of $99,000 with a standard deviation of $15,000.

• If we want to determine a 95% confidence interval for the average yearly income, what is the value of t?


• Develop a 95% confidence interval for the average yearly income of all pilots.