Question: Measuring intelligence in children: Mental measurements in children are often given by giving them blocks and telling them to build a tower as tall as possible. One experiment in block building was repeated a month later, with the times listed in the accompanying table.

a. Is there sufficient evidence to support the claim that there is a difference between the two times? Use a 0.01 significance level.

b. Construct a 99 percent confidence interval for the mean of the differences. Do the confidence interval limits contain 0, indicating that there is not a significant difference between the times of the first and second trials?

Child A B C D E F G H I J K L M N O

1^st 30 19 19 23 29 178 42 20 12 39 14 81 17 31 52

2^nd 30 6 14 8 14 52 14 22 17 8 11 30 14 17 15