a) Explain the difference between the "independent" and "matched - pair" samples.

b) A clothing manufacturer purchased some new design sewing machines in the hope that production would be increased. The production records of a random sample of workers are shown below:

Worker Old Machine New Machine 28 36 36 40 27 25 25 32 38 32 36 32 40 41 29 38 32 35 10 20 26 11 28 33 12 32 36