It has been argued that first-born children tend to be more independent than later-born children. Suppose we develop a 25-point scale of independence and rate each of 20 first-born children and their second-born siblings using our scale. We do this when both siblings are adults, thus eliminating obvious age effects. The data on independence are as follows (a higher score means that the person is more independent):

Sibling Pair: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 First Born: 12 18 13 17 8 15 16 5 8 12 13 5 14 20 19 17 2 5 15 18 Second Born: 10 12 15 13 9 12 13 8 10 8 8 9 8 10 14 11 7 7 13 12

a. Analyze the data using Wilcoxon’s matched-pairs signed-ranks test.

b. What can you conclude?