Effects of cocaine on children-researchers conducted a study to assess the effects that occur when children are exposed to cocaine before birth. On a measure of spatial/mathematical skill at age 4, the 190 children born to cocaine users had a mean of 7.3 and a standard deviation of 3.0. The 186 children not exposed to cocaine had a mean score of 8.2 with a standard deviation of 3.0.
(a) Construct a 99% confidence interval for the difference of the means.
(b) Interpret the interval using the context of the problem.
(c) Is there sufficient evidence to conclude that spatial/mathematical skill is significantly affected by exposure to cocaine before birth? Why or why not?