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. They counted the number of electric fish species above and below the entrance point of a major tributary at 11 different river locations. Here's what they found: Tributary Upstream number of species Downstream number of species Ica 13 20 Jutai 14 16 Japura 8 8 Coari 6 7 Purus Manacapuru Negro Trombetas Tapajos 2222 10 15 4 5 22 22 21 17 15 18 Xingu Tocantins 24 11 20 13 (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? Use R to calculate an appropriate t-value to use in 95% confidence interval formula. Carry out the rest of the calculation by hand (show working; 3 marks total) (b) Test the hypothesis that tributaries have no effect on the number of species of electric fish. Carry out the calculations by hand apart from the P-value. Calculate the P-value in R. Report the null and alternative hypotheses. State your conclusions about whether tributaries affected the local number of electric fish (show working; 3 marks) (c) State the assumptions that you had to make to complete parts (a) and (b) (1 mark).