In the normal distribution with any given mean and standard deviation, we know that approximately 68% of the observations fall within one standard deviation of the mean 95% of the observations fall within two standard deviations of the mean 99.7% of the observations fall within 3 standard deviations of the mean. This is sometimes called the 68-95-99.7 Empirical Rule of Thumb. Using this rule, answer the following question: A study was designed to investigate the effects of two variables--(1) a student' s level of mathematical anxiety and (2) teaching method--on a student's achievement in a mathematics course. Students who had a low level of mathematical anxiety were taught using the traditional expository method. These students obtained a mean score of 450 with a standard deviation of 30 on a standardized test. Assuming that this is a normal distribution, what is the probability that a student, chosen at random, would have a score less than 450? 95% 50% 2.5% 47.5%