:4. In 1971, the National Assessmet of Educational Progress (NAEP) administered a reading test to a nationwide random sample of 1600 9-year olds. The average of the scores was 67.2 (out of 100), and the SD of the scores was 14 points. In 1975 the NAEP administered the same test to the members of another random sample of 1600 9-year olds. This time, the average score was 68.5, with the SD again being 14. There appears to have been some improvement. Or can this be explained as a chance variation? If you formulate a null and an alternative hypothesis in terms of a box model, and use the appropriate test statistic z, the P-value turns out to be closest to a. 1 in 5 b. 1 in 10 c. 1 in 200 d. 1 in 500 e. 1 in 1000