The pH levels of a random sample of 16 chemical mixtures from a process were measured, and

Question:

The pH levels of a random sample of 16 chemical mixtures from a process were measured, and a sample mean x- = 6.861 and a sample standard deviation s = 0.440 were obtained. The scientists presented a confidence interval (6.668. 7.054) for the average pH level of chemical mixtures from the process. What is the confidence level of this confidence interval?