A salesman paid 12 visits to his area sales manager and noted that he
had to wait for 10,15,20,17,11,25,30,27,36,40,5 and 26 minutes,
respectively, before being called in his office. The area sales manager
claims that the salesmen wishing to meet him do not have to wait for
more than 20 minutes before being called in. Using the sign test, verify
at 0.05 level of significance the claim made by the area sales manager.