SOLUTION: The mean of a distribution is 100 and the standard deviation is 10. Which of the following values is unusual? A.130 B.80 C.120 D.90 can you please explain how to do

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Question 667100: The mean of a distribution is 100 and the standard deviation is 10. Which of the following values is unusual?
A.130
B.80
C.120
D.90
can you please explain how to do this, i dont understand it.

Answer by ewatrrr(24785)   (Show Source): You can put this solution on YOUR website!
 
Hi,
Important to Understand z -values as they relate to the Standard Normal curve:
Below: z = 0, z = ± 1, z= ±2 , z= ±3 are plotted.
Note: z = 0 , 50% of the area under the curve is to the left and 50% to the right

For the normal distribution:
one standard deviation from the mean accounts for about 68.2% of the set
two standard deviations from the mean account for about 95.4% of the set****
and three standard deviations from the mean account for about 99.7%.
μ = 100 , σ = 10
A. 130 > 3 standard deviations from the mean...comparatived to the others listed ... UNUSUAL
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