The pH of a solution is measured eight times by one operator using the same instrument. She obtains the following data: 7.15, 7.20, 7.18, 7.19, 7.21, 7.20, 7.16, and 7.18.
(a) Calculate the sample mean.
(b) Calculate the sample variance and sample standard deviation.
(c) What are the major sources of variability in this experiment?