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 elecctric 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 12 different river locations. Here's what they found:Tributary - Upstream number of species - Downstream number of speciesIca - 14 - 19Jutai - 11 - 18Japura - 8 - 8Coari - 5 - 7Purus - 10 - 16Manacapuru - 5 - 6Negro - 23 - 24Madeira - 29 - 30Trombetas - 19 - 16Tapajos - 16 - 20Xingu - 25 - 21Tocantins - 10 - 12a) What is the mean difference in the number of species between areas upstream and downstream of the 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).