Biological Data Analysis: Homework 8

Due Tuesday, Oct. 28



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. Every year, volunteers count the number of breeding horseshoe crabs on beaches on Delaware Bay. Data from this survey are shown below. You want to know whether the number of breeding horseshoe crabs was different between 2011 and 2012. Which test do you think would be most appropriate: a Student's t-test; a paired t-test; or Wilcoxon's signed ranks test? Write a few sentences giving your reasons for choosing that test.

 
Beach              2011      2012

BennettsPier      35282     21814
BigStone         359350     83500
Broadkill         45705     13290
CapeHenlopen      49005     30150
Fortescue         68978    125190
Fowler             8700      4620
Gandys            18780     88926
Higbees           13622      1205
Highs             24936     29800
Kimbles           17620     53640
KittsHummock     117360     68400
NorburysLanding  102425     74552
NorthBowers       59566     36790
NorthCapeMay      32610      4350
Pickering        137250    110550
PiercesPoint      38003     43435
Primehook        101300     20580
Reeds             62179     81503
Slaughter        203070     53940
SoutBowers       135309     87055
SouthCSL         150656    112266
TedHarvey        115090     90670
Townbank          44022     21942
Villas            56260     32140
Woodland            125     1260

2. Now analyze the data using all three tests: Student's t-test; a paired t-test; and Wilcoxon's signed ranks test. You may use spreadsheets, web sites, or SAS. Give the P-values in a nice little table, and write a couple of sentences comparing the results of the tests.

3. Make a graph that summarizes the data from question 2 in what you think is the most effective way.



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This page was last revised October 22, 2014. Its URL is http://udel.edu/~mcdonald/stathw8.html