In order to test the precision of a new type of blood sugar monitor for diabetic patients, 20 randomly selected monitors of this type were used. A blood sample with 120 mg/dL was tested in each of these monitors, and the resulting readings are given in the following table.
117 116 121 120 122 117 120 120 118 119
118 123 119 123 119 122 118 122 121 120
(a) Obtain a 99% con?dence interval for the variance σ2.
(b) Is it reasonable to assume that the data follow a normal distribution?