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 hypothesized 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 image below.