Researchers atWolfson Children’s Hospital, Jacksonville, FL tested new technologymeant to reduce the number of attempts needed to draw blood from children.

They collected data on the number of successes on the first attempt using the new technology and on a historicalcomparison group using standard technology.

This data is summarized in Table 5.21.

Table 5.21 Data for Exercise 17 Standard Technology New Technology Successful on 1st 74 73 Unsuccessful on 1st 76 18 Total 150 91

(a) Is there evidence that the new technology changes the probability of a success on the first attempt? Is the change for the better or for the worse?

(b) The researchers also recorded the ages of the children. In the standard technology group, the 150 children had a mean age of 5.73 and a standard deviation of 6.15. In the new technology group, the mean age was 9.02 with a standard deviation of 6.10. Does the mean age of the children in the two groups differ significantly?

(c) How do the results of part

(b) complicate the interpretation of part (a)?

(Private communication, H. Hess, Wolfson Children’s Hospital, 2009.)

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