6.4 G*Power Calculation for ANOVA Sample Size

Activity 6.4 Instructions Document

6.4 G*Power Calculation for ANOVA Sample Size

Problem Narrative 6.4:

A major government contractor wants to find out what type of control interface will work best

for a new unmanned vehicle currently being developed for the U.S. Army. The typical control

interfaces that are available are 1) handheld video game/joystick controller, 2) Smart

phone/tablet controller, 3) integrated desktop joystick/keyboard/mouse controller, or 4)

augmented reality gesture-based controller. The researcher has done a literature search for this

type of research and would like to calculate the sample size needed. Based on the literature, the

researcher will be assuming an effect size of 0.40, alpha of 0.05, a desired power of 0.80, with

four groups.

Part I: G*Power Exercise: Using G*Power to Estimate Sample Size:

Use G*Power to estimate the sample size needed assuming the parameters listed above for a test

family of "F tests", a statistical test of "ANOVA: Fixed effects, omnibus, one-way", and Type of

power analysis of "A priori: Compute required sample size - given Alpha, power, and effect

size".

After you run your G*Power analysis and obtain your results, click on the “Protocol of Power

Analyses” tab at the top of your G*Power window. A window will appear with your parameters

and output. Select “Print” and print your G*Power output as a pdf file. Save this pdf file for

upload as one of your deliverables for this exercise. Name your pdf file “6.4 GPower Protocol

Output”.

Part II: Short Answer Questions:

Create an MSWord document to answer the short answer questions from part II and III of this

exercise. The name of the file will be “6.4 GPower Exercise – Short Answer Questions”. Save

this for subsequent upload as one of your deliverables for this exercise.

Answer the following questions using the narrative provided above and G*Power:

1. Is the assumed effect size small, medium, or large?

2. Is the desired power of 0.80 considered an adequate power for this research?

3. What is the estimated F critical calculated by G*Power

4. What are the dfnumerator and dfdenominator?

5. What is the total sample size needed?

6. What is the number of participants per group?

7. What is the actual power calculated by G*Power?

Part III: Results Write Up:

Write up the results of your data analysis in standard APA format being sure to mention all

relevant variables and findings in your write up. Make sure your format adheres to APA format

and guidelines. Save the document as “6.4 GPower Results Write Up”.

(If you have questions about what a complete results write up for a power analysis looks like,

either look up conference and journal articles that use t-tests as their statistical analysis or contact

your instructor for specific guidance.)

Your deliverables for this SPSS exercise will be:

1. The G*Power output file “6.4 GPower Protocol Output”.

2. The Short Answer document “6.4 GPower Exercise – Short Answer Questions”.

3. The APA formatted results write up “6.4 GPower Results Write Up”.

Upload all three of these files as your submission for this exercise to be considered for full credit.