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Suppose the difference in score (post minus pre) for all students who take the prep course is known to follow a normal distribution with a known population mean difference of 8 points and a known population standard deviation of 4 points. Also, suppose the next prep course will be taken by 16 students who can be considered a random sample. Which graph below best represents the model that could be used to approximate a probability about the sample mean difference in scores (post minus prej for the 16 students? Graph A Graph B Graph C Nonal a Graph A O Graph B u Graph C Again we have that an exam prep company states that students who take their prep course improve by an average of 8 points on a post test as compared to their pre-test score. Based on historical data, it can be assumed that the difference in score (post minus prej for all students who take the prep course folows a normal distribution (with some population mean difference ud and some population standard deviation og, both of which are not known). The prep course is taken by 16 students, which can be considered a random sampie. and resulted in a sample mean difference in score (post minus pre) of 10 points and a sample standard deviation (of the pairwise differences in each student's scores) of 4 points. Which graph below best represents the model that could now be used to approximate the probabilty that, assuming the company's statement is true, the resuiting sample mean difference in scores (post minus pre) for a random sample of 16 students will be 10 points or higher (that is, to approximate the probability that, assuming the company's statement is true, of getting a sample mean difference in scores (post minus pre) for a random sample of 16 students as large as 10 points or even larger)? Graph A Graph 8 Graph C Normal a Graph A a Graph B a Graph C Saved