Statistics Papers
scalet3
statistical_assignment_3.docxThe analysis of variance (ANOVA) is a collection of statistical tests of the differences between groups that is mathematically related to t-tests. In its basic form, ANOVA is a statistical test to see whether or not the means of several groups are equal. So, it generalizes t-tests of more than two groups or variables. If we wanted to see which of two classes had better test scores on a final exam, we might use a t-test; if we wanted to know which class in a large school had the best final exam score we might use the ANOVA analysis.
In Week Three, you will examine the one-way analysis of variance (ANOVA) and repeated measures design and compare those to the other tests of means from Week Two. You will also have an opportunity to discuss a research question as well as to evaluate the best test to use to address that question statistically.
Required Resources Read from the course text, Statistics for the Behavioral & Social Sciences :
· Chapter 6: Analysis of Variance
· Chapter 7: Repeated Measures Designs for Interval Data
Recommended Resources Article
Statgraphics Centurion. (2006). Analysis of variance. Retrieved from http://www.statgraphics.com/analysis_of_variance.htm
· This interactive website describes in detail how to use several types of ANOVA. It also includes examples and graphical displays.
Websites
1. VassarStats: Website for Statistical Computation . (http://vassarstats.net)
· This is a website includes tools to calculate many of the statistical tests we cover in this course including t-tests, ANOVA, correlation, and regression. Each calculator includes a tutorial and/or walkthrough.
2. Web Center for Social Research Methods. (http://socialresearchmethods.net)
· This website includes links to numerous tools and tutorials relating to statistical concepts, calculations, and scale development.
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ANOVA |
Due Thursday by 18:00 hours
In this 1 page paper, you will evaluate a research question and determine how that question might best be analyzed. To do this, you will need to identify the appropriate application of course specified statistical tests, examine assumptions and limitations of course specified statistical tests, and communicate in writing critiques of statistical tests.
A researcher wishes to study the effect of a new drug on blood pressure. Consider and discuss the following questions as you respond:
· Would you recommend using a z-test, a t-test, or an ANOVA for the analysis? Explain your answer.
· What would your choice of test depend on? For the test you select, explain your design and your comparison groups.
· Would the hypothesis be directional or non-directional?
· Would the test be one-tailed or two-tailed?
· What would be the null and what would be the alternative hypothesis?
· Provide references on separate page
This last part should be on a separate sheet of paper…alone with references.
How does the number of groups being compared affect the statistical analysis? What suggestions would you make for change or improvement? Why would these suggestions potentially be more useful?
Discussion 1 –ANOVA– Evaluate the methods, results, limitations, and assumptions of an article utilizing ANOVA. Examine the difference between one- and two-tailed hypothesis tests.
When grading the ANOVA discussion I will be looking for your answer to contain:
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Week 3 Paper 1 Board Rubric |
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Earned |
Weight |
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Content Criteria |
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0.5 |
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Student identifies the groups in their test for blood pressure. |
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Student identifies and defines which test they will use to test their groups. Provides support for why this test was chosen. |
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0.5 |
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Student defines one tailed and two tailed t-tests and identifies which is used in their experiment. |
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0.5 |
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Student defines directional and non-directional hypothesis and identifies which is used in their experiment. |
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0.5 |
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The student responds to at least two classmates’ initial posts by Day 7. |
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1 |
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Format |
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2 |
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Student uses correct spelling, grammar and sentence structure. |
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Total |
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5 |
Intellectual Elaboration:
Last week we looked at standard deviation and the z-score as ways to look at different data distributions but be able to compare them as equals and how inferential statistics work. This week we will look at inferential statistics, specifically the ANOVA.
Similar to the t-test is the Analysis of Variance (ANOVA) also allows us to statistically see if the independent variable(s) (IV) have an effect on the dependent variable (DV). Unlike the t-test the ANOVA allows us to look at more than one IV if needed to test for statistical effect. The one-way ANOVA is similar to the one way t-test, both are looking at the one DV and one IV to determine if there is any statistically significant change. The benefit of the ANOVA is that it will allow direct comparison of multiple groups (with multiple IV’s) instead of separate t-test for each comparison. Within an ANOVA a post-hoc test is used to determine which groups being tested are statistically different from one another (Tanner, 2012).
Repeated measures, also known as the within-subject design, in a ANOVA is how we test to see if the means are the same or different when we correlate data from subjects within the same groups instead of between groups (Choudhury, 2009). What this means is that you can test the mean of the same variable across different points of time, or you can test the mean of the same variable across different conditions (Lund Research, 2012). For example if testing the HIV drug you could test mean of the DV (white blood cell count) across a 3 month, 6 month, and 12 month period. If you want to test Drug X under different conditions you could test the drug alone, and paired with medication A and medication B. This test is an extension of the t-test and looks to see if there are differences within the mean(s) being tested. When looking at what the results mean when using repeated measures you will either accept the null hypothesis (there is no change) or choose the alternative hypothesis. The way you will do this is with a post hoc test or HSD (honesty significantly different). The HSD will give you the minimum difference between the two means being tested to determine if they are significantly different. If there is a statistical significance you will not accept the null hypothesis (Tanner, 2011).
Additional Resources (web links, videos, and articles):
ANOVA – With Independent Samples
http://www.youtube.com/user/EducatorVids2?v=NiAlbPv4pEQ&feature=pyv
Repeated Measures ANOVA:
https://statistics.laerd.com/statistical-guides/repeated-measures-anova-statistical-guide.php
References:
Choudhury, A (2009). Repeated Measures ANOVA. Retrieved from Experiment Resources: http://www.experiment-resources.com/repeated-measures-anova.html
ChangingMinds.org. (2012) t-test. Retrieved from http://changingminds.org/explanations/research/analysis/t-test.htm
Lund Research Inc. (2012) Repeated measures ANOVA. Retrieved from https://statistics.laerd.com/statistical-guides/repeated-measures-anova-statistical-guide.php
Tanner, D. (2011). Statistics for the behavioral & social sciences. San Diego, CA: Bridgepoint Education, Inc.
Assignment When you are writing your ANOVA Critique paper this week I want you to use the following format:
I. Introduction – What is an ANOVA and what is the research problem and hypothesis of the article?
II. Methods – Who are the subjects and variables within the article?
III. Results – What is the statistical analysis used, why were these tests chosen? What were the results of these tests and what do they mean?
IV. Discussion – What were the strengths of this article? What would you have done differently in terms of variables and statistical analysis? Why?
V. Conclusion – Reiterate the introduction and include relevant information that answers the questions regarding the hypothesis.
ANOVA Article Critique Read the article "Cognitive Effects of Risperidone in Children with Autism and Irritable Behavior," and identify the research questions and/or hypotheses as they are stated. Consider the following questions: What are the variables (sample sizes, population, treatments, etc.)? How was the analysis of variance used in this article (and what type of ANOVA was used)?
Write a two- to three-page paper presenting the information listed below. In addition, provide a title page and reference page in APA style. Cite any references made to the article within the body of the paper in APA style. Your paper should begin with an introductory paragraph (including a thesis statement) and end with a concluding paragraph summarizing the major points made in the body of the paper and reaffirming the thesis. Carefully review the Grading Rubric for the criteria that will be used to evaluate your assignment. The body of your paper must:
1. Determine what question(s) the authors are trying to answer by doing this research.
2. Determine the hypothesis being tested and the concepts that were applied in this process.
3. Evaluate the article and critique the statistical analysis employed in the study. Would you have included more and/or different variables? Explain your answer.
4. Examine the assumptions and limitations of the statistical study. What would you have done differently in this case? Explain your answer.
5. Identify how the authors applied statistical testing to the problem.
6. Interpret the findings of the author(s) using statistical concepts.
Access the Critical Thinking Community website for tips on how to formulate your thoughts and discussion of these questions in a logical and meaningful manner. Writing the Article Critique The Assignment:
1. Must be two to three double-spaced pages in length (excluding title and reference pages), and formatted according to APA style as outlined in the Ashford Writing Center.
2. Must include a title page with the following:
a. Title of paper
b. Student’s name
c. Course name and number
d. Instructor’s name
e. Date submitted
3. Must document all sources in APA style as outlined in the Ashford Writing Center.
4. Must include a separate reference page formatted according to APA style as outlined in the Ashford Writing Center.
5. Choudhury, A (2009). Repeated Measures ANOVA. Retrieved from Experiment Resources: http://www.experiment-resources.com/repeated-measures-anova.html
6. ChangingMinds.org. (2012) t-test. Retrieved from http://changingminds.org/explanations/research/analysis/t-test.htm
7. Lund Research Inc. (2012) Repeated measures ANOVA. Retrieved from https://statistics.laerd.com/statistical-guides/repeated-measures-anova-statistical-guide.php
