. At Rachels 11th birthday party, eight girls were timed to see how long (in seconds) they could hold their breath in a relaxed position. After a two-minute rest, they timed themselves while jumping. The girls thought that the mean difference between their jumping and relaxed times would be zero. Test their hypothesis

Relax time seconds:

26

47

30

22

23

45

37

29

Jumping time (seconds)

21

40

28

21

25

43

35

32