Arnold F. answered • 01/31/16
Tutor
5
(53)
College Professor & Expert Tutor In Statistics and Calculus
You need to use the transformation:
z=(x-mu)/sigma to turn each x-value into a standard normal variable and then use a normal table:
https://www.wyzant.com/resources/files/392716/normal_dist_table
to get the corresponding area (probability).
It helps if you sketch the graph and shade in the area you are looking for.
You can use this technique for the other questions you posted here as well.
Need more help> Comment back.
Arnold F.
To get the z-value for x=17 : z=(17-20)/5 = -.6
Looking .6 up in the table gives: 0.2258 but this is the area between -.6 and 0. You want the area on the other side of -.6 which would be .5 - .2258 = .2742.
So P(x<17) = P(z<-.6) = .2742 .
For P(20<x<28) = P(z1 < z < z2) , calculate z1 and z2 and try to find the appropriate probabilities. Hint: z1=0 since (20-20)/5 = 0 and z2 = (28-20)/5 .
Report
01/31/16
Jeffrey D.
01/31/16