Ecn 221 Based on the average predictions of 47 members of the National Association of Business Economists (NABE), the U. S. gross domestic product (GDP) will expand by 3.2% in 2011 (The Wall Street Journal, May 23, 2010). Suppose the sample standard deviation of their predictions was 1%. At a 5% significance level, test if the mean forecast GDP of all NABE members is greater than 3%.