An article gave the following summary information for fracture strengths (MPa) of n = 196 ceramic bars fired in a particular kiln: x = 54.31, s = 3.02
Suppose the investigators had believed a priori that the population standard deviation was about 4 MPa. Based on this supposition, how large a sample would have been required to estimate ? to within 0.5 MPa with 95% confidence?