Question: According to the local union president, the mean gross income of plumbers in the Salt Lake City area is normally distributed, with a mean of $30,000 and a standard deviation of $3,000. A recent investigative reporter for KYAK TV found, for a sample of 18 plumbers, the mean gross income was $30,500. At the .10 significance level, is it reasonable to conclude that the mean income is not equal to $30,000? Show all 5 steps.