Attention time given to twins. Psychologists have found that twins, in their early years, tend to have lower IQs and pick up language more slowly than nontwins (Wisconsin Twin Research Newsletter, Winter 2004). The slower intellectual growth of most twins may be caused by benign parental neglect. Suppose it is desired to estimate the mean attention time given to twins per week by their parents.

A sample of 50 sets of 212-year-old twin boys is taken, and at the end of 1 week, the attention time given to each pair is recorded. The data (in hours) are listed in the following LO6 table. Find a 90% confidence interval for the mean attention time given to all twin boys by their parents. Interpret the confidence interval.

20.7 16.7 22.5 12.1 2.9 23.5 6.4 1.3 39.6 35.6 10.9 7.1 46.0 23.4 29.4 44.1 13.8 24.3 9.3 3.4 15.7 46.6 10.6 6.7 5.4 14.0 20.7 48.2 7.7 22.2 20.3 34.0 44.5 23.8 20.0 43.1 14.3 21.9 17.5 9.6 36.4 0.8 1.1 19.3 14.6 32.5 19.1 36.9 27.9 14.0