This paper aims to test the module ILOs using a practical real-life case-study. In this case study, you are going to play the role of an analyst for one of the corporates, let us call it Company-Z. Therefore, let us first introduce the case-study random variables: is the Company-Z monthly revenue along the period Pre-COVID-19(January 2018 to December 2019); is the same Company-Z monthly revenue but during the period Post-COVID-19(March 2020 to September 2020); is the monthly operations cost during the period Pre-COVID-19(January 2018 to December 2019); while is the same monthly operations cost but during the period Post-COVID-19(March 2020 to September 2020). Accordingly, in your analysis, you will depend on two main random variables over two time series. The first random variable is the Company-Z monthly revenue , and the second random variable is the Company-Z monthly operations cost . The two random variables were chosen over two periods of time: the first is (Pre-COVID-19: January 2018 to December 2019), and the second is (Post-COVID-19: March 2020 to September 2020). Your task is to prepare a comprehensive report to the company, fulfilling specific requirements outlined below in point (3).

1. What are the 95 percent confidence intervalsfor the average monthly operations cost Pre- and Post- COVID-19 ? And what do you conclude by comparing these intervals? Moreover, what is the used methodologyof constructing the confidence interval for each random variable, and why did you use the proposed methodology for each random variable?