In an investigation of the techniques used by two different laboratories for the dating of prehistoric cereal seeds, 10 pairs of seeds were used. Each pair had been found close together at the same site; one seed from each pair was dated by laboratory A and the other by laboratory B. The table shows the ages in years.

Site 1 2 3 4 5 6 7 8 9 10

Lab. A 10124 10672 9491 10848 9277 9217 9294 10584 9983 10004

Lab. B 9902 10680 9474 11044 9315 9344 9696 10571 9712 10009

i) Is there any evidence of a systematic difference in the ages returned by the two laboratories?

ii) Give a 90% confidence interval for the mean difference between the age returned by laboratory A and the corresponding age returned by laboratory B?

are they independent?