Isopods Lab  


  • To recognize the diversity of experimental designs that can be used to test a single hypothesis 
  • To understand the difference between descriptive and inferential statistics 
  • To understand the difference between common statistical tests 
  • To practice designing experiments with consideration of the specific inferential statistic used before collecting the data 
  • To practice critically evaluating experimental designs 


Isopods prefer moist environment than dry environment 


If isopods prefer a moist environment, then when given a choice, more individuals will move towards the wet side than to the dry side.  

Null hypothesis

Isopods do not have a preference between wet and dry soil.

Materials and Methods

  • 5 groups of 5 isopods 
  • Stopwatch 
  • Dry potting soil 
  • Wet potting soil 
  • Plastic container (6in X 4in)

Five of the sowbugs from holding were randomly selected and placed into a beaker upside in the plastic container. The beaker was removed and the sowbugs were allowed to roam for three minutes. At three minutes the number of sowbugs in the wet mound, dry mound, or between the mounds was recorded. These five sowbugs were placed into a different holding container to avoid reuse in subsequent trials. This was repeated four more times for a total of five trials that each had new randomly selected sowbugs for observation.

Observed frequencies table:

Trial Number (3min intervals) Isopods in Wet Isopods in Dry Not in Either
1 2 3 0
2 2 1 2
3 4 0 1
4 2 3 0
5 5 0 0

Table 1: Describes five different 3min trail on the number of Isopods located in three different environments 

The averages:

Average in Wet Average in Dry Average in Neither
3 1.4 0.6

Table 2: Describes the average number of isopods located in the three different environment 



Base upon observation, there were more Isopods present in the wet soil than dry soil and neither soil. 

Standard deviations were larger in the between and dry groups suggesting a greater variance for these environments compared to the smaller variation that was calculated for the wet environment. The wet environment had the greatest average of sow bugs found during this experiment. The Kruskal-Wallis test found H=-44.47 which is not significant at p=0.009.


Photo by Martin Cooper is licensed under CC BY 2.0

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