Instruction 8-3 A Quality Control Engineer Is Interested in the Mean Length

Short Answer

Instruction 8-3
A quality control engineer is interested in the mean length of timber poles being cut automatically by machine. The desired length of the insulation is 12 metres. It is known that the standard deviation in the cutting length is 0.15 metres. A sample of 70 cut poles yields a mean length of 12.14 metres. This sample will be used to obtain a 99% confidence interval for the mean length cut by machine.
-Referring to Instruction 8-3,the critical value to use in obtaining the confidence interval is _________ .