Question

4. A study of mercury levels in two species of fish yielded the following results (in parts per million) Species Sample size Sample mean Sample standard deviation Whiting 23 Flathead 18 6.14 7.78 2.23 3.14 You may assume both samples came from normal populations and are independent (a) Is there sufficient evidence to ustify claiming that a difference exists in the mean mercury levels between the two species? Use 0.05 and clearly state your null and alternate hypotheses (b) Give a 95% confidence interval for the mean difference in the mercury levels between the two species (c) Is there evidence that the population variances of the mercury levels differ between the two species? Use a 0.05 and clearly state your null and alternate hypotheses The following R output may be useful > t-c (0.005 ,0 . 01 , 0.025 ,0.05, 0.950, 0.975, 0.990, 0.995) >qchisq(t,24) [1] 9.886 10.856 12.401 13.848 36.415 39.364 42.980 45.559 > qchisq(t,23) [1] 9.26 10.20 11.69 13.09 35.17 38.08 41.64 44.18 >qt (t,43) [1] -2.695-2.416 -2.017 -1.681 1.681 2.017 2.416 2.695 > qt (t,41) 1] -2.701-2.421 -2.020 -1.683 1.683 2.020 2.421 2.701 qt (t,39) 1 -2.708 -2.426 -2.023 -1.685 1.685 2.023 2.426 2.708 > qf (t,23,18) 1] 0.3146 0.3531 0.4177 0.4819 2.1587 2.5151 3.0161 3.4228 > of (t,22,17) [1] 0.3054 0.3439 0.4085 0.4731 2.2084 2.5855 3.1192 3.5552 > qf (t,17,22) 11 0.2813 0.3206 0.3868 0.4528 2.1138 2.4478 2.9082 3.2748

Answer 1