Question 1:

Using a TI-84 Plus calculator, find the area under the standard normal curve to the right of the following z-values. Round the answers to at least four decimal places.

(b) Find the area under the standard normal curve to the right of =z2.28.

The area to the right of =z2.28 is blank.

Question 2:

Using the TI-84 Plus calculator, find the area under the standard normal curve that lies between the following z-values. Round the answers to at least four decimal places.

(b) Find the area under the standard normal curve that lies between =z0.42 and =z0.23.

The area between =z0.42 and =z0.23 is blank.

Question 4:

Check our blood pressure: In a recent study, the Centers for Disease Control and prevention reported that diastolic blood pressures of adult women in the United States are approximately normally distributed with mean 80.3mmHg and a standard deviation of 9.7mmHg. Round the answers to four decimal places.

(d) Is it unusual for a woman to have a blood pressure lower than 68 mmHg ?

It is blank unusual because the probability of a woman having blood pressure lower than 68 mmHg is blank.

Question 5:

How many apps? According to a website, the mean number of apps on a smartphone in the United States is 91. Assume the number of apps is normally distributed with mean 91 and standard deviation 26.

(a) What proportion of phones have between 55 and 98 apps? Round the answer to four decimal places.

The proportion of phones that have between 55 and 98 apps is blank .

Question 6:

Tree heights: Cherry trees in a certain orchard have heights that are normally distributed with mean =113 inches and standard deviation =11 inches. Use the TI-84 PLUS calculator to answer the following. Round the answers to at least four decimal places.

(a) What proportion of trees are more than 131 inches tall?

(b) What proportion of trees are less than 98 inches tall?

(c) What is the probability that a randomly chosen tree is between 90 and 105 inches tall?

Question 7:

Tire lifetimes: The lifetime of a certain type of automobile tire (in thousands of miles) is normally distributed with mean =39 and standard deviation =6. Use the TI-84 Plus calculator to answer the following.

(a) Find the 19th percentile of the tire lifetimes.

(b) Find the 71st percentile of the tire lifetimes.

(c) Find the first quartile of the tire lifetimes.

(d) The tire company wants to guarantee that its tires will last at least a certain number of miles. What number of miles (in thousands) should the company guarantee so that only 2% of the tires violate the guarantee?

Round the answers to at least two decimal places.