Question: A carbon monoxide testing sensor is being calibrated against a known standard of 5ppm CO. The following readings were obtained from the equipment:

4.5, 5.3, 4.7, 4.6, 5.1, 4.6, 4.7, 4.5.

Could you be 95% confident that these readings came from population mean of 5? Put another way, do you have evidence to suggest that the machine was not working properly?