A cell phone company offers two plans to its subscribers. At the time new subscribers sign up, they are asked to provide some demographic information. The mean yearly income for a sample of 40 subscribers to Plan A is $59,100 with a standard deviation of $9,200. For a sample of 30 subscribers to Plan B, the mean income is $63,000 with a standard deviation of $7,100.
At the .01 significance level, is it reasonable to conclude the mean income of those selecting Plan B is larger? Hint: For the calculations, assume the Plan A as the first sample.
The test statistic is ???? . (Negative amount should be indicated by a minus sign. Round your answer to 2 decimal places.)