The following measurements ( in picocuries per liter ) were recorded by a set of helium gas detectors installed in a laboratoryfacility: 383.6, 347.1, 371.9, 347.6, 325.8, 337 Using these

measurements, construct a 90% confidence interval for the mean level of helium gas present in the facility.Assume the population is normally distributed. Step 1. Calculate the sample mean for the given sample data. (Round answer to 2 decimal places) Step 2. Calculate the sample standard deviation for the given sample data. (Round answer to 2 decimal places) Step 3. Find the critical value that should be used in constructing the confidence interval. (Round answer to 3 decimal places) Step 4. Construct the 90% confidence interval. (Round answer to 2 decimal places)