Question 1105766
Level of significance is 0.01.  
Ho=no change
Ha:there is some change from the previous value
I would use a two-tailed test because it's not clear which way the change is gone, and a two-tailed test is more conservative.
use a z-test, because sigma is known, and critical value is |z(0.995)|> 2.576
z=(change in mean)/sigma/sqrt(n)
=942*sqrt(38)/1904=3.05
This is greater than the critical value, so there is strong evidence at the 1% level that there is a difference. There has been a significant increase in the average sales and they are now more than they used to be.