stats ch 8

The mean of the t distribution is _____. a. 0 b. dependent upon the sample size c. .5 d. 1

A

A random sample of 144 observations has a mean of 20, a median of 21, and a mode of 22. The population standard deviation is known to equal 4.8. The 95.44% confidence interval for the population mean is _____. a. 19.2 to 20.8 b. 15.2 to 24.8 c. 21.2 to 22.8 d. 19.216 to 20.784

A

If the margin of error in an interval estimate of μ is 4.6, the interval estimate equals _____. a. x̄ ± 4.6 b. x̄ ± 4.508 c. x̄ ± 6.9 d. x̄ ± 2.3

A

It is known that the variance of a population equals 1,936. A random sample of 121 has been selected from the population. There is a .95 probability that the sample mean will provide a margin of error of _____. a. 7.84 or less b. 344.96 or less c. 31.36 or less d. 1,936 or less

A

The t distribution is a family of similar probability distributions, with each individual distribution depending on a parameter known as the _____. a. degrees of freedom b. finite correction factor c. sample size d. standard deviation

A

Using α = .04, a confidence interval for a population proportion is determined to be .65 to .75. If the level of significance is decreased, the interval for the population proportion _____. a. becomes wider b. does not change c. becomes narrower d. Not enough information is provided to answer this question.

A

As the sample size increases, the margin of error _____. a. increases b. decreases c. stays the same d. None of these answers are correct.

B

For the interval estimation of μ when σ is assumed known, the proper distribution to use is the_____. a. t distribution with n degrees of freedom b. standard normal distribution c. t distribution with n − 2 degrees of freedom d. t distribution with n − 1 degrees of freedom

B

A sample of 26 elements from a normally distributed population is selected. The sample mean is 10 with a standard deviation of 4. The 95% confidence interval for μ is _____. a. 6.000 to 14.000 b. 8.462 to 11.538 c. 8.384 to 11.616 d. 9.846 to 10.154

C

If we want to provide a 95% confidence interval for the mean of a population, the confidence coefficient is _____. a. 1.645 b. .485 c. .95 d. 1.96

C

In determining an interval estimate of a population mean when σ is unknown, we use a t distribution with _____ degrees of freedom. a. √n-1 b. n c. n − 1 d. √n

C

The z value for a 97.8% confidence interval estimation is _____. a. 2.00 b. 2.02 c. 1.96 d. 2.29

D