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A real estate agent wants to estimate the average selling price of homes in a neighborhood. She collects random sample data from 8 recent home sales and finds that the sample mean selling price is $350,000 with a sample standard deviation of $25,000. Assuming home prices in the neighborhood are normally distributed, construct a 95% confidence interval for the population mean selling price.

A financial analyst is studying the average return on investment (ROI) for a particular stock. He randomly selects data from 30 investors and finds that the sample mean ROI is 6.2% with a population standard deviation of 1.5%. Construct a 90% confidence interval for the population mean ROI.

An economist is analyzing monthly utility expenses for households. He collects data from 12 households and calculates a sample mean monthly expense of $180 with a sample standard deviation of $15. He also notes that the distribution of utility expenses is heavily skewed to the right. Construct a 90% confidence interval for the population mean monthly utility expense.