Finding Normal Distribution Probability

X~N(23,11). P(X>20) =

(Give your answers to 3sf)

(Hint: Annex A for keystrokes)

X~N(1, 2). P(|X|<2) =

(Give your answers to 3sf)

(Hint: Page 4 of notes)

X~N(7, 3). P(X<m) = 0.125

m = ?

(Give your answers to 3sf)

(Hint: Refer to Annex for keystroke)

• N(4,6)

• N(4,12)

• N(5,6)

• N(5,12)

Let X~height of a randomly chosen woman. X~N(160, 4) If, M=\frac{X_1+X_2+X_3+X_4}{4} , M~ ? (Hint: Page 13 of notes)

• N(160,4)

• N(160,1)

• N(40,4)

• N(40,1)

28% of all Woodrow students believe Monday will be snow day. You take a sample of 50 students and find that 15 of them believe Monday will be a snow day. (The sample proportion is 15/50 or .3) What is the probability of getting a sample of size 50 that has 15 or more students who believe Monday will be a snow day?

• 0.376

• Cannot be determined because the distribution of the sample proportion of samples of size 50 is not normal

• 0.624

• 0.99999

78% of flights on major airlines arrive on time. A random sample was taken of 100 flights. Find the probability that more than 70% of the 100 randomly selected flights are on time.

• 0.5077

• 0.0267

• 0.9999

• 0.9733

• p = 0.3085

• p = 0.6687

• p = 0.4104

• p = 0.3354

Find the proportion of the normal distribution that is associated with z > -0.50

• p = 0.6915

• p = 0.3085

• p = 0.1915

• p = 0.6950

Answer explanation

Drawing a distribution, you will notice that the proportion of the distribution that is greater than z = -0.50 exceeds .50, meaning we will find our answer in the B (Body) column of our unit normal table. Afer matching our z = -0.50 to the B column, we should get a proportion of p = 0.6915.