5.23 The output of a group of 11 workers before and after an improvement in the lighting in their factory is as follows: Before 52 60 58 58 53 51 52 59 60 53 55 After 56 62 63 50 55 56 55 59 61 58 56 Test whether there is a significant improvement in performance

(a) assuming these are independent samples,

(b) assuming they are dependent.