In a law office the average number of billed hours per day w

In a law office, the average number of billed hours per day was 148 last year. In the first 72 days of this year, the average number of billed hours per day is 157 with a standard deviation of 63 hours. When testing the hypothesis (at the 10% level of signficance) that the average number of billed hours per day has increased, what test statistic? (please round your answer to 2 decimal places)

Solution

              
Getting the test statistic, as              
              
X = sample mean =    157          
uo = hypothesized mean =    148          
n = sample size =    72          
s = standard deviation =    63          
              
Thus, z = (X - uo) * sqrt(n) / s =    1.212183053   = 1.21 [answer]