Using the Text find the proportion of the total area identif

Using the Text find the proportion of the total area identified with the following statements:

above a z score of 1.28

between the mean and a z score of 1.28

below a z score of - 1.0

Solution

a)

Using a table/technology, the right tailed area of this is          
          
P(z >   1.28   ) =    0.100272568 [answer]

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b)

z1 = lower z score =    0      
z2 = upper z score =     1.28      
          
Using table/technology, the left tailed areas between these z scores is          
          
P(z < z1) =    0.5      
P(z < z2) =    0.899727432      
          
Thus, the area between them, by subtracting these areas, is          
          
P(z1 < z < z2) =    0.399727432   [answer]

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c)

Using a table/technology, the left tailed area of this is          
          
P(z <   -1   ) =    0.158655254 [answer]