A random sample of 30 households was selected as part of a study on energy usage in a small community, and the number of kilowatt-hours (kWh) was recorded for each household in the sample for the March quarter of 2020. The data were approximately normally distributed with a mean of 375 kWh and a sample standard deviation of 85. A researcher intends to determine a 99% confidence interval for the population mean electricity usage during the period. Respond to the prompts that follow. (1 point each)

1. Will this confidence interval calculation be based on a z-interval or a t-interval? What is the rationale for that?
2. What is the point estimate for the confidence interval and how did you determine this?
3. What is the critical value of z or t to be used and the df, if required?
4. Describe how to calculate the standard error SE and show the calculations using the data for this scenario.
5. Assuming that usage is normally distributed, calculate a 99% confidence interval for the community's mean electricity usage in the March quarter of 2020.