Stat 538 - Biostatistics I - Fall 2005

   Homework 1, due in Lab Thurs Sept 8th


  1. The following observations are the lengths in days that 6 patients
     stayed in a hospital: 8, 10, 6, 12, 2, 10.

    (a) Compute by hand the following summary statistics: mean, median,
        variance, standard deviation, 25th and 75th percentiles, and the 
        inter-quartile range. You can use a calculator to take square roots, 
        divide, etc.  Make sure to report the units for each summary.

    (b) Enter the data in Minitab; verify that the calculations in (a) are 
        relatively close to those obtained via Minitab.  Minitab "interpolates"
        to get the quantiles which is just a little fancier than what we
        discussed in class.


  2. Use Minitab  to create a bar graphs of the data in Example 2.2 of
     SW, page 12. Order the bars in two ways:  As given in the text (in the order
     of strength of reaction), and in decreasing order of frequency (so the bars go
     from highest to lowest).  Say a few words about what the graph suggests.


  3. Do all calculations for this problem in Minitab, using the data in 
     Exercise 2.7 of SW, page 24. 

     (a) Compute the mean, median, standard deviation, and IQR.

     (b) Generate an individual values plot, dotplot, histogram, stem and leaf display, 
         and boxplot for the data. 

     (c) Describe the shape of the distribution, being sure to consider
         symmetry, skewness, presence of outliers, and modality.

  4. Do problem 2.61 page 56 of SW.  Use both histograms and boxplots to address the 
     question of which transformation best makes the data look symmetric.


   For problems 2 - 4, import the Minitab output into your favorite word processing 
   software (like Word). Using the software, write up your solutions to these problems. 
   You can intersperse your comments around the output, or have all the comments in one 
   location, but make sure to carefully point out what in the output you are referring 
   to in the discussion.