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**An Introduction To Statistical Power

This tutorial illustrates the relationship between statistical power and four features of the test situation. An applet allows the user to manipulate a factor and immediately see the effects on other factors.
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Date Of Record Creation 2004-03-10 13:28:00
Date Last Modified 2010-04-07 11:57:00
Date Of Record Release 2004-07-27 10:45:00
Email Address
Resource Type
Author Name Dale Berger
Author Organization Claremont Graduate University, Claremont, CA
Technical Requirements Java capable browser
Comments This complete "ready-to-go" lesson is a nice supplemental resource for introducing the basic concepts of statistical power, a concept which is frequently difficult for students. Using this activity in combination with additional practice problems should help students solidify their understanding of these concepts.
Content Quality (Concerns) The definition of power is not located on the exercise pages. Initially, the complexity of the applet may be overwhelming for introductory students. For instance, it does not show how power is calculated. Instead, the numerical value of power for a given example is provided based on the values that are typed into the parameter boxes. This is fine if students have already learned what power is. Because students enter parameter values (i.e., sample size, null hypothesis mean) into boxes, they may need help connecting these boxes to real situations. Wording on the worksheet describing the color of the region on the applet associated with the values of the sample mean that lead to rejecting/not rejecting the null hypothesis could be misleading.
Content Quality (Strengths) This worksheet is well-written, factually correct, and statistically sound. It covers important issues, such as differences in power and practical significance.
Ease of Use (Concerns) Faculty might need to spend time explaining the graphics and the interface to students. On first exposure it is a bit overwhelming, since the graphic area has three graphs, two colors, and many different parameter boxes to manipulate. Additionally, some students may have difficulty reading the worksheets and extracting the necessary information.
Ease of Use (Strengths) The handouts are consistent with well-written, step-by-step instructions. Assuming students have the necessary equipment, this activity should progress smoothly for the students with very little preparation needed by the teacher.
Potential Effectiveness (Concerns) Students may be tempted to complete the assignment without thinking about the underlying concepts. In order to receive maximum benefits from using this activity, students need to be highly motivated, independent learners. The user should be aware that time to complete the activity could be a concern depending on the constraints of the given class.
Potential Effectiveness (Strengths) The well-labeled instructions direct the students' focus by having them manipulate one parameter at a time. This methodical process and the visualization provided by the applet help students build intuition and think critically about power, its implications, and how it is affected by certain factors. The graphics, typical of many textbooks, help tie these relationships to the mathematical underpinnings. Summary questions force students to recast their conclusions in a more general context.
Content Quality (Rating) 4
Ease of Use (Rating) 4
Potential Effectiveness (Rating) 4
Source Code Available On
Material Type
Statistical Topic
Intended User Role
Math Level

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