Answer:
68% of the time, John's grades will be between 55 and 85, while for Jane, 68% of the time, her grades will be between 65 and 75. They have the same mean grade, however, due to the lower standard deviation, Jane is more consistent, while John has the higher upside.
Step-by-step explanation:
The Empirical Rule states that, for a normally distributed random variable:
Approximately 68% of the measures are within 1 standard deviation of the mean.
Approximately 95% of the measures are within 2 standard deviations of the mean.
Approximately 99.7% of the measures are within 3 standard deviations of the mean.
John:
Mean of 70, standard deviation of 15.
70 - 15 = 55
70 + 15 = 85
68% of the time, John's grades will be between 55 and 85.
Jane:
Mean of 70, standard deviation of 5.
70 - 5 = 65
70 + 6 = 75.
68% of the time, Jane's grades will be between 65 and 75.
Describe the two students in terms of consistency of their grades and give reason.
68% of the time, John's grades will be between 55 and 85, while for Jane, 68% of the time, her grades will be between 65 and 75. They have the same mean grade, however, due to the lower standard deviation, Jane is more consistent, while John has the higher upside.
