High school students from track teams in the state participated in a training program to improve running times. Before the training, the mean running time for the students to run a mile was 402 seconds with standard deviation 40 seconds. After completing the program, the mean running time for the students to run a mile was 368 seconds with standard deviation 30 seconds. Let X represent the running time of a randomly selected student before training, and let Y represent the running time of the same student after training. Which of the following is true about the distribution of X-Y? a. The variables X and Y are independent, therefore, the meanis 34 seconds and the standard deviation is 10 seconds.
b. The v ales X and Y are independent therefore, the meanis 34 seconds and the standard deviation is 50 seconds
c. The variables X and Y are not independent, therefore, the standard deviation is 50 seconds and the mean cannot be determined with the information given.
d. The variables and are not independent, therefore, the meanis 3 seconds and the standard deviation cannot be determined with the information given
e. The variables X and Y We not independent, therefore, neither the mean nor the standard deviation can be determined with the informantion given.