Inference about Two Means: Independent Samples 2) A study was conducted to assess the effects that occur when children are exposed to cocaine before birth. Children were tested at age 4 for object assembly skill, which was described as "a task requiring visual-spatial skills related to mathematical competence." The 200 children born to cocaine users had a mean of 7.9 and a standard deviation of 3.2. The 190 children not exposed to cocaine had a mean score of 8.7 with a standard deviation of 3.1. Use a 0.05 significance level to test the claim that prenatal cocaine exposure is associated with lower scores of four-year-old children on the test of object assembly. Do not assume that the population standard deviations are equal.