Comparing Two Means”
Assignment 12—Questions from Chapter 12 “Comparing Two Means”, Part 1
(50 pt)
- Please type your final answers to the problems on the main pages of your assignment. After the pages with typed answers, attach handwritten pages showing your calculations. On the pages of calculations, clearly indicate the problem numbers and final answers. Don’t use computers for the analyses unless the problems say to.
- Directions for reporting results of statistical tests—on the typed pages, report:
–The means of each group
–n (sample size)
–degrees of freedom
–alpha (Threshold level of significance. Decide on the value before doing the statistical test. The default is to test at alpha = 0.05, meaning at the 5% significance level.)
–the name and value of the test statistic (Example: X2 value = 0.55)
–p-value (from a table of critical values in the back of the textbook)
–Describe your conclusion in a sentence. (Example 1: “Births are not evenly distributed over the days of the week.” Example 2: “The proportion of wild-type flies was significantly greater than expected by the 3:1 ratio.” Example 3: “The proportions of people who are interested in each of the five areas of psychology are significantly different.”
- For practice problems, please write an answer in your own words before checking your answer against the solutions in the back of the book. Then, compare the solution to your answer. If your answer wasn’t correct, don’t change it–write about how the solution in the book differed from your answer and why it’s correct. In other words, show evidence that you are thinking independently and learning. In this way, you can get full credit even if you originally didn’t have the correct answer.
- On graphs, include:
- Your name
- The assignment and number to the problem
- Include labels on the axes.
- Include units. Examples of units: cm or sec.
- Above or below the graph, write a figure legend that describes what data are in the graph. Include the sample size in the legend. See Endres and Lohmann (2012) fig 2 and fig 3 for examples. This article is in the folder “Assignments”. Reading the whole article won’t be part of this course—just look at the design of the graphs and legends. These graphs have standard error bars, which are not part of histograms.
- At the end of the figure legend, write in parentheses the names of the authors and year published for the source of the data—you don’t want to represent the data as your own. Example of citation: (data from Cratsley and Lewis (2003)). The authors for the data are listed in problems. It’s really important to make it clear that data aren’t yours if you’re showing them to other people.
Chapter 12 Practice Problems
2a (4 pt)
2b (4 pt)
4 all (8 pt) See the handout “More about how to do a t-test” in D2L “Copies of Handouts”. It contains info on determining whether a test should be unpaired or paired.
7 (2 pt)
11a (10 pt) Do by hand and show your work. Follow the directions for statistical tests. Don’t use Excel. You can attach pages with hand-written calculations. (Keep about three significant digits or else the rounding errors magnify when squared.) Assume normality.
11b (2 pt)
12a (4 pt)
12b (4 pt)
12c (4 pt)
12d (4 pt)
Assignment Problems, Chapter 12
24 (4 pt)
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At the end of your paper, please write “Number of hours I spent on this homework:” and add an estimate. Don’t include time that you spent reading the chapter. This number won’t affect your grade.
