P(172 < x <192)

Question

the random variable x is normally  distributed  with  mean  u = 174 and standard  deviation = 20. Find the indicated probability. 

 

 

 

 

 

P(172 < x <192)

Answer 1

mean = 174, sd = 20

find z scores for 172 and 192

(172-174)/20 = -4/20 = -1/5 = -0.2

(192-174)/20 = 18/20 = 9/10 =0.9

now find the areas under the curve for both then add them

use z tables

= .079 +.316 = .395 so

Pr(172 < x < 192) = about 39.95 %