Research Paper: Power and Sample Assignment


The purpose of this assignment is to demonstrate your ability to determine and justify your sample size. Research conducted with too small of a sample size cannot be adequately trusted as valid and poses a greater risk of incorrectly rejecting the null hypothesis.  Researchers cannot simply make up a sample size that seems to make sense to them, nor use a sample size simply because it is a large number. Therefore, in more advanced research, an a priori sample size is determined before conducting the research to determine if the research can be conducted, if a sufficient sample size can be obtained, and other important factors needed in advance before proceeding with research. For example, this information is also often required to create budgets and apply for grants where funds must be justified based on calculated need rather than “guesstimations”.  While you also should conduct a post hoc power analysis to determine the strength of your study, an a priori power analysis gives you the information you need to proceed with your study.


Install G*Power/Calculate a Priori Power and Sample Size

For this assignment, you will need to first download and install the G*Power software ( This is available as a free download.

Calculate Power

To complete the assignment, you will use this software to calculate the a priori power for your study. You can choose any statistical test appropriate to your study to calculate this, and it is understood that you are still developing your project. Therefore, you may need to repeat this to calculate additional a priori power analyses for your final paper. The point of this assignment is to demonstrate that you are able to calculate them and justify the proposed details of your study.

To calculate this, use a=.05 and a priori power minimum effect of .80.  You will utilize previous studies to gain information on supporting and calculating your a priori power and minimum sample size.

Present results

After calculating your power, you should submit an APA formatted paper with a title page and reference page. Use an appropriate APA formatted level I heading to organize your paper and identify each section to your reader.

In the body of your paper, you should begin with with identification of your initial hypotheses and variables for your reader so that your information makes sense in context. These will be revised in later assignments, but you should include what you have in mind at this point.

Then include a summary of the sample size and power (where given) used in previous studies from a minimum of 3 to 5 articles to support the development of your needed sample size. Provide sufficient details from the articles, summarized into one or more paragraphs in this section, to use as a background for your G*Power calculations.

Finally, provide a detailed and clear narrative of the findings of your G*power calculations.  Be sure to include your rationale for what you entered, what the results tell you and your reader, and how you will use this information to determine your sample size and recruit participants for your study. If you do not plan to use participants in your study (such as historical or document research), create this assignment as though you were planning to use participants.  This section should also include the graphic output from your G*power analysis.   For this part of the assignment, you can either use a clear and legible screen clip of your output, or create your own table, formatted in APA, to present your findings. Be sure that your table reflects all of the information provided in the G*power output. 

Your submission should include all of the following:

  • your hypotheses and variables as planned at this point
  • a summary of the power and sample size justifications used in previous studies
  • a narrative and graphic output of your G power calculations indicating your intended sample size based on your a priori determination

-Paper must be in current APA format, including a title page and reference page

-Your assignment will be checked for originality via the Turnitin plagiarism tool.

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