Quality control in manufacturing plan randomly selected sample of n=9 ready for shipment items and c

Quality control in manufacturing plan randomly selected sample of n=9 ready for shipment items and checked parameters Sample average was found as ?x =40 with a sample standard deviation of s=12 Construct a 90% confidence interval for the population mean This is the case when population standard deviation is unknown For Margin of Error use t-value from Appendix Table for t-Distribution