The National Assessment of Educational Progress (NAEP) administered a reading test to a nationwide probability sample of 9-year-olds in 2010. The same test was administered to an independently chosen sample of 9-year-olds in 2020. There appears to have been some improvement: in 2010, the average score was 68.3 out of 100, while in 2020 the average score was 69.0 out of 100. Or could this be explained as a chance variation? Explain your reasoning. You may assume the NAEP took independent simple random samples in 2010 and 2020;