Answer:
a) 68%
b) 95%.
c) 2.5%
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.
In this problem, we have that:
Mean of 100,000, standard deviation of 10,000.
a. Approximately what percentage of the salaries fall between $90,000 and $110,000?
90,000 = 100,000 - 10,000
110,000 = 100,000 + 10,000
Within 1 standard deviation of the mean, so approximately 68%.
b. Approximately what percentage of the salaries fall between $80,000 and $120,000?
80,000 = 100,000 - 2*10,000
120,000 = 100,000 + 2*10,000
Within 2 standard deviations of the mean, so approximately 95%.
c. Approximately what percentage of the salaries are greater than $120,000?
More than 2 standard deviations above the mean.
Approximately 95% of the measures are within 2 standard deviations of the mean, so approximately 5% are more than 2 standard deviations from the mean.
The normal distribution is symmetric, which means that 2.5% are more then 2 standard deviations below the mean, and 2.5% are more than 2 standard deviations above the mean, which means that 2.5% of the salaries are greater than $120,000.
