A random sample of n, 20 winter days in Denver gave a sample mean pollution index x, = 43. Previous studles show that o,- 10. For Englewood (a suburb of Denver), a random sample of n, - 19 winter days...

Extracted text: A random sample of n, 20 winter days in Denver gave a sample mean pollution index x, = 43. Previous studles show that o,- 10. For Englewood (a suburb of Denver), a random sample of n, - 19 winter days gave a sample mean pollution Index of x, = 37. Previous studies show that g, -13. Assume the pollution Index is normally distributed in both Englewood and Denver. Do these data indicate that the mean population pollution index of Englewood is different (either way) from that of Denver in the winter? Use a 1% level of significance. (a) what is the level of significance? State the null and alternate hypotheses. (b) what sampling distribution will you use? What assumptions are you making? O The Student's t. We assume that both population distributions are approximately normal with unknown standard deviations. O The Student's t. We assume that both population distributions are approximately normal with known standard devtations. O The standard normal. We assume that both population distributions are approximately normal with unknown standard devlations. O The standard normal. We assume that both population distributions are approximately normal with known standard devtations. What is the value of the sample test statistic? (Test the difference u, - l. Round your answer to two decimal places.) ) Find (or estimate) the Pvalue. (Round your answer to four dectmal places.) Sketch the sampling distribution and show the area corresponding to the P-value. US O O 8:29 -> #3 2$ & 8 9. %D 4.