mean = 20 standard deviation 10 find area between x1 = 15 & x2= 40

Question

MBA assignment question.

Answer 1

(x1-20)/10=-5/10=-0.5; (x2-20)/10=2.

So we have z1=-0.5 and z2=2 (these are the number of standard deviations from the mean).

Assuming a normal distribution, p(-0.5)=0.3085; p(2)=0.9772, so p(15<X<40)=0.6687 or 66.87%. This is the probability of data lying between 15 and 40.