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

 

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