#### SamuelMartin

##### New Member

Prob( X < mean + 1.5*σ) = 0.9332

Prob( X < mean + 0.5*σ) = 0.6915

Prob( X < mean + 1.5*σ) - Prob( X < mean + 0.5*σ) = 0.9332 - 0.6915

Problem:

Assume that a random variable follows a normal distribution with a mean of 50 and a standard deviation of

10. What percentage of this distribution is between 55 and 65?

a. 4.56%

b. 8.96%

c. 18.15%

d. 24.17%

Answer: d.

Explanation:

Prob(mean + 0.5*σ < X < mean + 1.5*σ) = Prob( X < mean + 1.5*σ) - Prob( X < mean + 0.5*σ)

= 0.9332 - 0.6915 = 0.2417

THANK YOU VERY MUCH!!!!