For this assignment, you need to use a web applet that calculates power, manipulate the numbers as described below to see how that affects power, and then write a short (225 to 250 words long) paper. You must submit the paper in Webcourses in Microsoft Word format (.doc or .docx) and screenshot captures of your calculation of the power by the due date. The calculation of power screenshots can be cut-and-pasted at the end of your paper. Your paper and the power analyses must be your own work. I will be using Turnitin.com to check for plagiarism.
Hypothetical Scenario:
Pretend you are a psychologist planning a study on the effect of motivation on performance on an attention task. In this task, participants try to identify target letters in a stream of letters passing by at a rapid rate. You know from long experience that, under ordinary experimental conditions, the population of students who participate in this task identify a mean of 71 of the key letters, that the standard deviation is 10, and that the distribution is approximately normal. You predict that, if the participant is paid a dollar for each letter identified correctly, the number correctly identified will increase to 74. Your original plan is to test 20 participants under these conditions using the .05 significance level.
Using the Power & Sample Size Calculator to find power:
Go to: https://www.stat.ubc.ca/~rollin/stats/ssize/n1.html
Select Calculate Power (for specified Sample Size)
Enter the values for the mu0 (known population mean), mu1 (predicted sample mean), sigma (Ï which is the known population standard deviation), ? (sig. level), and sample size (N). The value for Power is what is being calculated and doesnât need to be entered by you (leave that box empty). Also, make sure to choose 1 Sided Test.
Click on Calculate and you should now see the resulting Power. This will be your original value for Power.
Take a screen capture to save this analysis (see instructions below if you don’t know how to do this)
Demonstrating the Practical Ways of Increasing Power (see Table 6-6 in textbook):
Predicted difference between population means (m0-m1): Change the value for mu1 to be 80 and leave everything else the same, click on Calculate and notice the change in Power, and take a screen capture to save this analysis.
Now, put the original value of mu1 back in and click on Calculate to reset the Power back to its original value.
Standard deviation (Ï): Change sigma to be 5, notice the change in Power, and take a screen capture to save this analysis.
Now, put the original value of sigma back in and click on Calculate to reset the Power back to its original value.
Sample size (N): Change n to be 25, notice the change in Power, and take a screen capture to save this analysis.
Now, put the original value for n back in and click on Calculate to reset the Power back to its original value.
Significance level (α): Change ? to be .01, notice the change in Power, and take a screen capture to save this analysis.
Now, put the original value for ? back in and click on Calculate to reset the Power back to its original value.
Now, using trial-and-error and putting in increasing values for the sample size and clicking on Calculate, figure out how much higher N needs to be in order to have a power level of 80%. Take a screen capture to save this analysis.
Screen Capture:
How to do a screen capture on a Mac: https://www.cnet.com/how-to/mac-screenshots-4-ways-to-capture-your-macbooks-screen/
How to do a screen capture in Windows 10: https://www.cnet.com/how-to/8-ways-you-can-take-screenshots-in-windows-10/
After you create the screen capture, you can insert the image into your Word document as a picture. Make sure your screen capture shows the finished analysis (all of the proper numbers show be shown).
APA Style Paper:
Write a brief (225 to 250 words long) summary of your analyses. In the paper, you should write from the perspective of being the researcher yourself and include the following:
Explanation of what the study was about â you must write as if you are the researcher conducting the study in the hypothetical scenario above, but you must use your own words to explain things. Donât just copy the paragraph I gave you, but make sure you are using the same basic scenario.
Report of each modification you made and the resulting change in the power
Report how many more participants you would need to use in order to have a power level of 80% and how you figured that out
Give your thoughts about the Power & Sample Size Calculator. Did it help you understand how the various factors affect power?
APA Style: Please refer to pp. 212-214 to see how power is discussed in research articles.
For this assignment, you need to use a web applet that calculates power, manipul
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