Widget, Inc. manufactures a certain type of metallic bar with tensile strength of 88 kilograms with a standard deviation of 3.5 kilograms. Several of its customers have complained about excessive variability of tensile strength of recently purchased bars

As part of an investigation to check the validity of these complaints, a Black Belt has performed destructive testing on 23 samples from a recent production batch and obtained a standard deviation of 3.8 kilograms.

a) Calculate a 95% confidence interval for the standard deviation of tensile strength.

b) Are the concerns from the customers valid?