Question: Mental measurements of young children are often made by giving them blocks and telling them to build a tower of 10 blocks. This experiment was repeated twice with five randomly selected children, and the time it took each child the task provided in the following table:

CHILD 1st TRIAL 2nd TRIAL

Sally 30 30

Carol 178 52

Jeremy 42 14

Winston 39 8

Meagan 31 17

At the 1% significance level, do these data prove that the mean time to complete the task is less on the second trial? Assume the population of paired differences has a normal distribution. Use the critical value approach.