Assume that you have a normal distribution of IQ scores with

Assume that you have a normal distribution of IQ scores with a mean of = 100 and a standard deviation of =8. WHAT PROPORTION OF THE CASES HAVE AN IQ SCORE ABOVE 108?

A. 0.2104

B. 0.8881

C. 0.3119

D.0.3413

Solution

We first get the z score for the critical value. As z = (x - u) / s, then as          
          
x = critical value =    108      
u = mean =    100      
          
s = standard deviation =    8      
          
Thus,          
          
z = (x - u) / s =    1      
          
Thus, using a table/technology, the right tailed area of this is          
          
P(z >   1   ) =    0.158655254 [ANSWER]

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