Kay L.

asked • 08/05/17

Find: P(38< = X < = 45 when mu = 40, sigma = 2.5

P(38< = X < = 45 when mu = 40, sigma = 2.5

1 Expert Answer

By:

Kenneth S. answered • 08/05/17

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Z45= (45-40)/2.5 = 2
Z38 = (38-40)/2.5 = -2/2.5 = -4/5 = -0.8
 
P(X<45) = 0.97725
P(X<38) = 0.21186
 
Therefore P(38 < X < 45) is the difference of the above two decimal values.  Go figure!
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Kay L.

when i calculate in excel i get the below does this look accurate? Thank you!
 
Probability for a Range
From X Value 38
To X Value 45
Z Value for 38 -0.8
Z Value for 45 2
P(X<=38) 0.2119
P(X<=45) 0.9772
P(38<=X<=45) 0.7654
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08/05/17

Kenneth S.

Looks OK...the only difference is that my table gave 5 decimal place values, yours gave 4 DP.
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08/06/17

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