Biological Data Analysis: Homework 3

Due Tuesday, Sept. 20

You must type this and all other homework assignments. Do not e-mail the assignment to me; turn it in early (at 322 Wolf) for a foreseeable absence, or turn it in late after an unexpected absence from class.

1. Download the Homework 3 spreadsheet. It contains some of the data you and your classmates collected (you'll analzye the measurement variables in later homework assignments). Use the exact test, chi-square test, and G-test of goodness-of-fit to test the following statistical null hypotheses for the data you personally collected (probably about 8 individuals):

the P-value for each statistical test of each null hypothesis, in a nice little table. The table should include the raw data (number of right and left) and the three P-values.

2. Test the three null hypotheses again using all three statistical tests, but this time use the entire data set (483 observations). Report the results in a table like for question 1. In class on Thursday, I demonstrated how to count things by sorting and then selecting. Another method is to use the COUNTIF function in Excel. For example, to count the number of males, you would find an empty cell and enter


3. Download G*Power for Windows or G*Power for Mac. Following the instruction near the bottom of the exact test web page, determine the sample size you would need for an experiment to detect a difference of 20 percent between the observed number of people with left arm on top, and the expect proportion if the null hypothesis were true. Then estimate the sample size needed if the difference was 10 percent; 5 percent; 3 percent; and 1 percent. Report the sample sizes needed and any other information you think is relevant.

4. The last pictures I showed before class are from a trip I took 10 years ago, and I can remember each day of the trip in vivid detail. But I couldn't tell you much about what I was doing two weeks ago. Biological statistics is a very important part of your life, of course, but it shouldn't be the only thing you do. Do something fun and adventurous and exciting and interesting this weekend, so fun and so adventurous that you'll remember it 10 years from now. If you have the kind of fun adventure you can tell me about, then tell me about it; if you have the kind of fun you'd like to keep private, then don't tell me about it.

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