A machine makes catheters for use in heart tests. The machine is designed so that the mean diameter of the catheter it makes can change but the standard deviation can't. The population standard deviation is .05 mm. Right now the machine is supposed to be making catheters with a mean diameter of 2 mm. During production an inspector checks the diameter of catheters to see if the machine has slipped out of the adjustment. A random sample of 50 catheters is taken. If the mean diameter for the sample is 2.04 mm, does this indicate the machine has slipped out of adjustment and the population average diameter of the catheter is no longer 2mm. The best test to use in this situation is a