To compare the impacts of roads in two adjacent ecoregions in Brazil researchers sampled stretches of roadway over a period of 7 years in each region and recorded the species of animals killed by vehicles. In the-Atlantic Forest habitat there were 178 roadkills observed, of which 51 were six-banded armadillos (Euphractus sex-cinctus). In the adjacent Cerrado habitat, there were 318 roadkills observed, of which 66 were six-banded armadillos. Use a chi-square test to assess the evidence that six-banded armadillos make up different proportions of species killed for the two regions.
(a) State the null hypothesis in words.
(b) State the null hypothesis in symbols.
(c) Compute the sample proportion of six-banded armadillos killed among roadkills in each ecosystem and display the results in a table similar to Table 10.1.2.
(d) Create a table displaying the observed and expected counts.
(e) The value of χ2s = 3.948 and the non directional P-value is 0.047. If α = 0.05, what are your conclusions?
(f) Based on these findings, would it be reasonable to surmise that six-banded armadillos are in more danger of being hit at one location than the other, or is further information needed? If so, what information would be helpful?