Researchers studying the number of electric fish species living in various parts of the Amazon basin were interested in whether the presence of tributaries affected the local number of electric fish species in the main rivers (Fernandes et al. 2004). They counted the number of electric fish species above and below the entrance point of a major tributary at 12 different river locations. Here’s what they found:

a. What is the mean difference in the number of species between areas upstream and downstream of a tributary? What is the 95% confidence interval of this mean difference?

b. Test the hypothesis that the tributaries have no effect on the number of species of electric fish.

c. State the assumptions that you had to make to complete parts (a) and (b).

Transcribed Image Text:

Tributary IçáLAA Jutai Jutaà Japurá Japurà CoariCoari Purus Purus ManacapuruManacapuru NegroNegro Madeira Madeira Trombetas Trombetas Tapajós TapajÚ XinguXingu TocantinsTocantins Upstream number of species 1414 1111 88 55 1010 55 2323 2929 1919 1616 2525 1010 Downstream number of species 1919 1818 88 77 1616 66 2424 3030 1616 2020 2121 1212