Question

Exercise 4. (20pts) Chocolate Bar Calories The average number of calories in a 1.5-ounce chocolate bar is 225. Suppose that the distribution of calories is approximately normal with σ = 10 . Find the probability that a randomly selected chocolate bar will have. (4a) Between 200 and 220 calories. Draw picture (4b) Less than 200 calories

Answer 1

solution

given that

(A)

P(200< x <220 ) = P[(200-225) /10 < (x - ) / < (220-225) /10 )]

= P(-2.5 < Z < -0.5)

= P(Z <-0.5 ) - P(Z <-2.5 )

Using z table   

= 0.3085-0.0062

probability= 0.3023

(B)

P(X<200 ) = P[(X- ) / < (200-225) /10 ]

= P(z <-2.5 )

Using z table

= 0.0062

probability=0.0062