22.46 24.10 8.48 20.28 22.04 24.32 26.02 20.09 21.95 23.77 26.12 27.87 21.67 23.59 25.46 27.88 29.67 23.21 25.19 27.11 29.59 31.42 24 7 7 9. (35 points) A researcher designs an experiment to test whether indoor plants make a difference in bacterial concentration in the air. They use 25 rooms, each with the same number of plants in them, and 27 rooms without any plants. The bacteria concentration is measured after a week. The mean concentration in rooms with plants is 1 = 125 with a sample standard deviation of s] = 21, and the mean concentration in rooms without plants is 12 = 115 with a sample standard deviation of $2 = 16.3. (a) State the null and alternative hypotheses. (b) Calculate the value of the test statistic. (c) Estimate the P-value or find the cut-off value. Is the result significant at the level a = 0.05? Explain. amse-owl d) Calculate a confidence interval for the difference of mean bacterial concentration in the two types of rooms