2. the following measurements (in picocuries per liter) were recorded by a set of argon gas detectors installed in a research facility: 831.7, 847.2, 820.9, 826.3 using these measurements, construct a 95% confidence interval for the mean level of argon gas present in the facility. assume the population is approximately normal. step 3. find the critical value that should be used in constructing the confidence interval. round your answer to three decimal places.