Answer:
0.15% of the students spent more than 557 on textbooks in a semester
Step-by-step explanation:
The Empirical Rule states that, for a normally distributed random variable:
68% of the measures are within 1 standard deviation of the mean.
95% of the measures are within 2 standard deviation of the mean.
99.7% of the measures are within 3 standard deviations of the mean.
In this problem, we have that:
Mean = 473
Standard deviation = 28
According to the standard deviation rule, almost 0.15% of the students spent more than what amount of money on textbooks in a semester?
99.7% of the measures are within 3 standard deviations of the mean, so 100 - 99.7% = 0.3% are more than 3 standard deviations from the mean.
The normal distribution is symmetric, which means that 0.3%/2 = 0.15% spend less than 3 standard deviations below the mean, and 0.15% spend more than 3 standard deviations above the mean.
473 + 3*28 = 473 + 84 = 557
0.15% of the students spent more than 557 on textbooks in a semester
