Are children heavier now than they were in the past? The National Health and Nutrition Examination Survey (NHANES) published in 2005 reported that the mean weight of six-year-old girls in the United States was 50.3 pounds. Another NHANES survey, published in 2013, reported that a simple random sample of 178 six-year-old girls had an average weight of 52.9 pounds. Assume the population standard deviation is = 18 pounds. Can you conclude that the mean weight of six-year-old girls is higher in 2013 than in 2005? Use the critical value method and the = 0.05 level of significance.