Question

Find the following probabilities for the standard normal random variable ?:

(a)  ?(−2.3≤?≤0.91)=

(b)  ?(−0.21≤?≤0.42)=

(c)  ?(?≤0.94)=

(d)  ?(?>−1.13)=

Answer 1

Solution

Using standard normal table

a) P ( -2.3 Z 0.91)

P ( Z 0.91 ) - P ( Z -2.3 )

= 0.8186 - 0.0107

= 0.8079

Probability = 0.8079

b ) P (−0.21 Z 0.42)

P ( Z 0.42 ) - P ( Z −0.21)

= 0.6628 - 0.4168

= 0.2460

Probability =0.2460

c ) P ( Z 0.94 )

=0.8264

Probability = 0.8264

d ) P ( Z > −1.13)

1 - P ( Z < −1.13)

= 1 - 0.1292

= 0.8708

Probability =0.8708