- #1
Biochemgirl2002
- 30
- 1
- Homework Statement
- Suppose X ~ N(20, 25). Determine the following
probabilities.
(A) P(X < 18)
(B) P(X > 27)
(C) P(13 < X < 23)
- Relevant Equations
- if X~N(mean, standard deviation squared) then,
z=(x-mean)/(standard deviation)~N(0,1)
a) P(X<18) = (18-20)/sqrt25
=-2/5
=-0.4
then you use the standard normal table and find that;
P(X<18)=0.3446
b) P(X>27)
= (27-20)/5
= 7/5
= 1.4
P(Z>1.4)
=P(Z<-1.4)
=0.0808
C) =(13<X<23)
=13-20/5 , 23-20/5
=-7/5 , 3/5
=-1.4 , 0.6
P(Z<0.6)-P(Z<-1.4)
=0.7257-0.0808
=0.6449
=-2/5
=-0.4
then you use the standard normal table and find that;
P(X<18)=0.3446
b) P(X>27)
= (27-20)/5
= 7/5
= 1.4
P(Z>1.4)
=P(Z<-1.4)
=0.0808
C) =(13<X<23)
=13-20/5 , 23-20/5
=-7/5 , 3/5
=-1.4 , 0.6
P(Z<0.6)-P(Z<-1.4)
=0.7257-0.0808
=0.6449
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