Let x be a random variable representing the SAT math score of student. We may assume that x has a normal distribution and that the population standard deviation is 25. A large university claims the average SAT math score for incoming freshman is 650. You suspect that this claim is too high and decide to test the claim. You select a random sample of 75 incoming freshman and find the mean SAT math score to be 645. If you assume that the population mean is 650, find the standardized test statistic based on the sample.