Biological Statistics
Homework 5
Due Tuesday, Oct. 9

  1. Collect some attribute data and summarize it in a table. You must have one attribute variable with two values, and the other with at least four values (like the bird sex ratio data from homework 4, only don't use that data, because that would be boring). Your data set could be a published data set, some data you've collected for your research, or some data you collect for this assignment. Your data should be at least somewhat biological; right-handed vs. left-handed players on four sports teams would be acceptable, Nike-wearing vs. Adidas-wearing would not. If you can't think of anything else, you could collect tree leaves (in at least four categories, such as four different trees) and observe whether each one has insect damage (visible holes or chewed-away edges) or not.
  2. Give a biological question that could be answered with your data from part 1, state the biological null hypothesis and the statistical null hypothesis, and analyze the data using the appropriate statistical test.
  3. Plot two bar graphs of the data you collected. On one, use error bars to represent the 95 percent confidence intervals found using the exact binomial calculation. On the other graph, use the error bars to represent the 95 percent confidence intervals based on the normal approximation.
  4. Collect some measurement data. You must have one attribute variable with at least four values (such as undergraduate, graduate, post-doc, faculty, or dog, cat, bunny, ferret) and one measurement variable (such as nose width or number of fleas). You must have at least ten observations in each of your four or more categories. Your data set could be a published data set, some data you've collected for your research, or some data you collect for this assignment. If you can't think of anything else, you could collect tree leaves (in at least four categories, such as four different trees) and measure their length.
  5. Put your raw data (the individual observations) in a table. For each category, calculate the mean, median, range, standard deviation, standard error of the mean, and 95 percent confidence interval. Add these summary numbers to the table. Then draw a bar graph, with vertical columns representing the means and thin vertical lines representing the 95 percent confidence intervals. Your graph should have a legend underneath it, explaining what it is.
    Keep a copy of your measurement data; you'll need it for the next homework assignment.

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This page was last revised October 4, 2007. Its URL is http://udel.edu/~mcdonald/stathw5.html