Question 28

Which of the following is true about normal curves?

The area underneath the curve is equal to 1.5.

They are all bell shaped.

They all have mean 0.

Question 31

An automobile battery manufacturer claims that its midgrade battery has a mean life of 50 months with a standard deviation of 6 months. Suppose the distribution of battery lives of this particular brand is approximately normal.

Find the probability that a randomly selected battery of this type will last less than 44 months.

Normal Distribution Calculator:Links to an external site.

0.68

0.13

0.16

Question 32

An automobile battery manufacturer claims that its midgrade battery has a mean life of 50 months with a standard deviation of 6 months. Suppose the distribution of battery lives of this particular brand is approximately normal.

Find the probability that a randomly selected battery of this type will last between 44 and 50 months.

Normal Distribution Calculator:

0.34

0.68

0.95

Question 35

An automobile battery manufacturer claims that its midgrade battery has a mean life of 50 months with a standard deviation of 6 months. Suppose the distribution of battery lives of this particular brand is approximately normal.

Find the probability that the mean of a random sample of 9 batteries of this type will last less than 44 months.

Normal Distribution

0.16

0.5

0.13

Question 37

Approximately 60% of all part-time college students in the United States are female. A random sample of 100 students is taken from the population of all part-time students in the United States, 50 of students were female.

Find the sample proportion the female part-time students ().

100

0.5

0.6

Question 39

Approximately 60% of all part-time college students in the United States are female. A random sample of 100 students is taken from the population of all part-time students in the United States, 50 of students were female.

What is probability that the sample proportion () is less than 60%?

Normal Distribution Calculator:Links to an external site.

0.5

0.95

0.1

Question 40

The Central Limit Theorem (CLT) says that the sampling distribution of the sample mean is approximately normal if . . .

all possible samples are selected.

the sample size is large.

the standard error of the sampling distribution is large.