While measuring specimens of nylon yarn taken from two spinning machines, it was found that 9 specimens from the first machine had a mean denier of 9.17 with a standard deviation of 1.81, while 12 specimens from the second machine had a mean denier of 7.33 with a standard deviation of 1.48. Test at the 0.05 level of significance that the mean denier of the first machine is higher than that of the second machine by at least 1.5.