Question

find p(65<X<70)

Answer 1

since mean and std deviation is not given we will solve in general form :

lets us say the mean = m

and std. deviation = s

z = (x-m)/s

for x=65

z1 = (65-m)/s

for x=70

z2 = (70-m)/s

using the table below :

from the table we will get P(z<z1) and P(z<z2)

P(x<70) = P(z<z2)

P(x<65) = P(z<z1)

required : p(65<X<70)

therefore we get :

p(65<X<70) = P(x<70) - P(x<65)

p(65<X<70) = P(z<z1) - P(z<z2) {P(z<z1) , P(z<z2) from the table}

(please upvote)