How does each of the following affect the power of a planned study?

27. A larger predicted difference between the means of the populations will ______ power?

       A. increase

       B. decrease

       C. have no effect on

 

28. A larger population standard deviation will ______ power?

       A. increase

       B. decrease

       C. have no effect on

 

29. A larger sample size will ______ power?

       A. increase

       B. decrease

       C. have no effect on

 

30. Using a more extreme significance level (for example, 0.01 instead of 0.05) will ______ power?

       A. increase

       B. decrease

       C. have no effect on

For a given study, how do each of the following variables affect power?

a. Changing α from .05 to .01

INCREASE / DECREASE / NO CHANGE

b. Increasing the sample size

INCREASE / DECREASE / NO CHANGE

c. Increasing the effect size

INCREASE / DECREASE / NO CHANGE

d. Choosing a research hypothesis with a value closer to the null hypothesis

INCREASE / DECREASE / NO CHANGE

e. Changing from a one-tailed test to a two-tailed test

INCREASE / DECREASE / NO CHANGE

Which of the following is not a conclusion of the central limit​ theorem?

A) The distribution of the sample means ​will, as the sample size​ increases, approach a normal distribution.

B) The distribution of the sample data will approach a normal distribution as the sample size increases.

C) The standard deviation of all sample means is the population standard deviation divided by the square root of the sample size.

D) The mean of all sample means is the population mean μ.

a simple random sample of 60 items resulted in a sample mean of 80. The population standard deviation is  15.

1. Compute the 95% confidence interval for the population mean.

2. Assume that the same sample mean was obtained from a sample of 120 items. Provide

   a 95% confidence interval for the population mean.

3. What is the effect of a larger sample size on the interval estimate?