For self education purpose:

During the Covid-19 pandemic, working from home has become the norm. Because of this, many households face an increasing monthly electricity bill.

Mr. Tan is a research student at the Singapore University of Social Sciences, and his research focus is to examine the impact of Covid-19 on household electricity consumption. He hypothesised that the average monthly electricity bill in a household has increased more than $5 during the Covid-19 pandemic. In order to test his hypothesis, he collected the electricity bill data in 50 households in May 2020 when Singapore was during the circuit breaker period.

Mr. Tan also found that the mean and standard deviation of electricity bill in a household in May 2019 are $26 and $7, respectively.

In order to study the impact of Covid-19 on household electricity consumption, Mr. Tan intends to make a comparison of the average electricity bills in May 2019 and May 2020 in his analysis.

The data is given in the Excel data file "BUS105_electricity".

Refer to excel file download for Excel data file "BUS105_electricity". Download link: https://easyupload.io/36o6o7

(a) Describe the 90% confidence interval for the average electricity bill in a household in May 2020. Interpret the meaning of the 90% confidence. Discuss whether he can conclude that the average monthly electricity bill in a household during the Covid-19 pandemic is $5 greater than that before the Covid-19.

(b) Discuss whether your conclusion will change if you use a 99.99% confidence interval and the number of data is a quarter of the original data set. Explain your findings. How reliable is your conclusion in 1(a)?

(c) Apply an appropriate hypothesis test to determine if the average monthly electricity bill in a household during the Covid-19 pandemic is $5 greater than that before the Covid- 19 pandemic.

Refer to excel file download for Excel data file "BUS105_electricity". Download link: https://easyupload.io/36o6o7