Performing a power analysis allows the researcher to calculate adequate sample size. Why is this preferable to accomplish in the design phase of a quantitative study? (Select all that apply.)

Question

a. A sample of sufficient size maximizes the chance of detecting statistical significance.
b. Performing a power analysis increases the research's potential for publication.
c. Conducting a power analysis decreases the chance of a type I error.
d. Conducting a power analysis increases effect size.
e. The institutional review paperwork must include a maximum sample size.

Answer 1

ANS: A, E
The deciding factor in determining an adequate sample size for correlational, quasi-experimental, and experimental studies is power. Power is the capacity of the study to detect differences or relationships that actually exist in the population. Expressed another way, power is the capacity to correctly reject a null hypothesis. Often the minimum acceptable power for a study is 0.80. If a researcher does not have sufficient power to detect differences or relationships that exist in the population, one might question the advisability of conducting the study. Therefore, it is advisable to conduct the power analysis in the design phase so as to ensure an adequate sample size is obtained. One of the items required by the Institutional Review Board is a description of the subjects the researcher plans to use in the study. This includes the maximum number of subjects anticipated.