9.

Number of working hours per day

a) 8

39

48.75

b) 10

25

31.25

c) 12

16

20

d) >12

0

0

10.

Number of night shifts per week

a) 2

40

50

b) 3

29

36.25

c) 4

11

13.75

d) >4

0

0

11.

Any previous history of illness

a) yes

39

48.75

b) No

55

68.75