31. Using a two-tailed test instead of a one-tailed test will ______ power?

       A. increase

       B. decrease

       C. have no effect on

 

32. The comparison distribution for a t test for independent means is:

a.    distribution of differences between means. 

b.    Z distribution (that is, a normal curve). 

c.     Poisson distribution. 

d.    distribution of proportional variance scores

 

33. Which option explains why we would need to use a t-test instead of a z-test?

a.    The population mean is not known

b.    The population standard deviation is not known

c.     The sample mean is not known

d.    The sample standard deviation is not known

 

34. The main difference between a Z score and a t score is that:

a.    t scores are used when a study is analyzed with a one-tailed test.

b.    t scores are used when the population variance is unknown.

c.     t scores are used only when the sample size is greater than 30.

d.    t scores are used only when inferences are made about other samples.

 

35. As the sample size increases, the distribution of t-scores:

a.    looks less like the normal curve.

b.    looks more like the normal curve.

c.     becomes more negatively skewed.

d.    becomes more positively skewed.

 

The t distribution should be used whenever.

(a)  None of the answers is correct.

(b) the sample size is less than 30

(c)  the population is not normally distributed

(d) the sample standard deviation is used to estimate the population standard deviation

6. As the test statistic becomes larger, the p-value

(a) gets smaller

(b) becomes larger 

(c) stays the same, since the sample size has not been changed

(d) becomes negative.

7. To describe the sampling distribution of the sample proportion, we use

(a) The sample proportion 

(b) The population proportion 

(c) The population mean

(d) The population mean

8. When small samples are used to estimate a population mean, in cases where the population standard deviation is unknown and the original distribution is normal:

(a) There always will be a large amount of sampling error.

(b) the t-distribution must be used to obtain the critical value.

(c) the resulting margin of error for a confidence interval estimate will tend to be fairly small.

(d) the z distribution must be used to obtain the critical value.

Which of the following is not appropriate to use the z-confidence interval for μ.

a) The sample size is greater than 30.

b) The sample is based on a simple random sample (SRS).

c) The population standard deviation, σ, is unknown.

d) The variable has a Normal distribution.

e) All of the above are appropriate.