Question 2:[10 marks]

1. (a)Calculate the 90% confidence interval estimate of the average departure delay times for flights that departed from the NYC airports in 2013. Remember to define the variable of interest and state the distribution. Show all working.

1. (b)Assume that we want to be more confident that the true average is contained in the interval. Hence, we increase the confidence level to 95%. Without any calculation, explain what would happen to the confidence interval width and estimation precision if the confidence level is increased while all other factors remain the same.

2. We want to estimate theproportion of flights that departed from the NYC airports in 2013 which are delayed. There are two ways we can do this. We can either obtain a point estimate or calculate an interval estimate. Provide estimates using both methods. Use a 99% confidence level. Show all working, define variables and state the distribution as needed.