Question

1.The gasoline consumption of an engine has a normal distribution with mean 5 gallons. In four independent tests, the probability that the average gasoline consumption is over 5 gallons is

A.none of these

B.0.50

C.1

D.0

2.Time (in minute) spent using e-mail per session is normally distributed with a mean of 4.5 minutes. Let P be the probability that the sample mean in a random sample of 25 sessions is between 4 minutes and 5 minutes. Let Q be the probability that the sample mean in a random sample of 64 sessions is between 4 minutes and 5 minutes. Then,

A.none of these is correct

B.P < Q

C.P > Q

D.P = Q

3.The central limit theorem states that as sample size gets large enough,

A.the distribution of the population data values becomes the normal distribution

B.the distribution of the sample data values becomes the normal distribution

C.the sampling distribution of the population mean becomes the normal distribution

D.the sampling distribution of the sample mean becomes the normal distribution

4.For a sample of size 2 or above, which of the following statements about sample mean are true?

I. Both population mean and sample mean are random variables.

II. The population mean and the expected value of the sample mean are the same.

III. The population standard deviation of is larger than the standard deviation of the sample mean.

A.I and III

B.I, II and III

C.II and III

D.I and II

Answer 1