In a school district, all sixth grade students take the same standardized test. the superintendent of the school district takes a random sample of 26 scores from all of the students who took the test. she sees that the mean score is 130 with a standard deviation of 7.2344. the superintendent wants to know if the standard deviation has changed this year. previously, the population standard deviation was 16. is there evidence that the standard deviation of test scores has decreased at the α = 0.05 level? assume the population is normally distributed.