Consider the following context: Palisades University Medical Center is making a concerted effort to improve salaries for its hourly employees working in the hospital's low skill labor force. According to a recent though possibly premature press release from the human resources department, for this population, the (mean) average hourly wages for these workers is now $20, give or take $2, which represents the population standard deviation. Stacy the stats intern working in the chief operations officer collected a sample of the hourly wages for 36 such low skills workers, and found they had a sample mean hourly wage of $19. She is admittedly skeptical that the reported wages are at the reported level, though respectfully won't speculate if higher or lower than reported. Is the human resources department's claim reasonable, at the 1% level of significance?

What is the critical value, expressed without insignificant digits? Include any positive or negative sign.