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A fictitious plant ecologist sampled 90 shrubs of a dioecious plant in a forest, and each plant was classified as being either male or female. The ecologist was interested in the sex ratio and whether it differed from 50:50. The observed counts and the predicted (expected) counts based on a theoretical 50:50 sex ratio follow.
Note, it is not necessary to open or create a data file for this question.
Lets now extend this fictitious endeavor. Recent studies on a related species of shrub have suggested a 30:70 female:male sex ratio. Knowing that our plant ecologist had similar research interests, the authors contacted her to inquire whether her data contradicted their findings.
Here is a modified example from Quinn and Keough (2002). Following fire, French and Westoby (1996) cross-classified plant species by two variables: whether they regenerated by seed only or vegetatively and whether they were dispersed by ant or vertebrate vector. The two variables could not be distinguished as response or predictor since regeneration mechanisms could just as conceivably affect dispersal mode as vice versa.
Arrington et al. (2002) examined the frequency with which African, Neotropical and North American fishes have empty stomachs and found that the mean percentage of empty stomachs was around 16.2%. As part of the investigation they were interested in whether the frequency of empty stomachs was related to dietary items. The data were separated into four major trophic classifications (detritivores, omnivores, invertivores, and piscivores) and whether the fish species had greater or less than 16.2% of individuals with empty stomachs. The number of fish species in each category combination was calculated and a subset of that (just the diurnal fish) is provided.
Open the arrington data file.
Here is an example (13.5) from Fowler, Cohen and Parvis (1998). A field biologist collected leaf litter from a 1 m2 quadrats randomly located on the ground at night in two locations - one was on clay soil the other on chalk soil. The number of woodlice of two different species (Oniscus and Armadilidium) were collected and it is assumed that all woodlice undertake their nocturnal activities independently. The number of woodlice are in the following contingency table.
An invertebrate biologist investigating the frequency of banding and color patterns in coastal and hedgerow populations of the terrestrial snail Cepea nemoralis classified captured snails as being of one of four color patterns (banded yellow, non-banded yellow, banded pink an non-banded pink). The biologist was primarily interested in whether the frequency of color patterns was associated (related) to habitat. Her compiled findings are presented in the following table.