Let the random variable Q represent the number of students who go to a certain teacher's office hour each day. The standard deviation of Q is 2.2. Which of the following is the best interpretation of the standard deviation? А. On average, the number of students going to an office hour varies from the mean by about 2.2 students. B. For a randomly selected office hour, the number of students who will go is 2.2. C. For a randomly selected office hour, the number of students expected to go will vary from the mean by 2.2 students. D. For a random selection of office hours, the average number of students expected to go is 2.2. E. For a random selection of office hours, the E average number of students expected to go will vary from the mean by 2.2 students.

The standard deviation is a measure of spread, which gives how values deviate from the average or mean value of a particular distribution. Hence, the standard deviation is usually defined about the average value of a distribution.

Therefore, for a certain random variable representing the number of student who visits office hours, the standard deviation will be defined about the average or mean value of the random variable Q.

Thus, stated as ; number of students going to an office hour varies from the mean by 2.2 on average.