Use the empirical rule to find the following probabilities. Remember to draw a normal curve, label the x-values for 1, 2, and 3 standard deviations from the mean, and write in the probabilities between each standard deviation before answering the questions.
Suppose that the scores on a national achievement exam have a mean of 480 and a standard deviation of 90.
What score is 3 standard deviations above the mean?
What score is 2 standard deviations below the mean?
Approximately 68% will fall between ______ and ______.
Approximately 99.7% will fall between _____ and ______ .
What is the probability that a randomly selected student will score at least a 300? _____%
What is the probability that a student will score at most a 390?