Page 53 - Basic Statistics

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 12 - 20 
b. P ( X < 12 ) =  Z P  
 5 
= P ( Z < -1.6 )

= P ( Z > 1.6 )

= 0.5 - P ( 0 < Z < 1.6 )

= 0.5000 – 0.4452 = 0.0548

Worked Example 3: Given a normal distribution with  = 40 dan  = 6.
Calculate the value of x that its area below 38%.

Worked Solution: Two exemplary previously completed work from the value

of x to z values and then proceed to calculate the area desired. In this example

we reverse the process, start with the opportunities or the area is known, then
calculate the value of z and the last determines the value of x by altering the

formula

x − 
z = make x =  z + 


Figure 3.9 P ( Z < z ) = 0.38

~~* CHAPTER 3 NORMAL PROBABILITY DISTRIBUTION *~~