Time

Grouping

n

0 level

1 level

2 level

3 level

4 level

Prior treatment

Observation group

90

0

15

39

24

12

Control group

90

0

16

37

26

11

Z value

0.041

P value

0.968

Posttreatment

Observation group

90

11

29

30

15

5

control group

90

5

23

32

22

8

Z value

2.040

P value

0.042