the press 21.40 The power of positive thinking? Does the way depicts the economic future affect the stock market? To investigate this, researchers analyzed the longest article about the crisis from the front page of the Money sec- tion of USA Today from a randomly chosen weekday of each week between August 2007 and June 2009. Articles were rated as to how positive or negative they were about the economic future. For each week, the change in the Dow Jones Industrial Average (average DJIA value the week after the article appeared minus the average the week the article appeared) was computed. Positive values of the change indicate that the DJIA increased.2" Here are the changes in DJIA corresponding to very positive articles: DJIA - 325 -200 -225 -75 -25 25 50 225 25 -225 -250 200 250 75 Here are the changes in DJIA values corresponding to very negative articles: 150 300 225 125 -175 -225 -375 - 175 125 175 475 Is there good evidence that the DJIA performs differ- ently after very positive articles than after very negative articles? (a) Do the sample means suggest that there is a differ- ence in the change in the DJIA after very positive articles versus after very negative articles? (b) Make stemplots for both samples. Are there any ob- vious departures from Normality? (c) Test the hypothesis Ho: u = 2 against the two- sided alternative. What do you conclude from part (a) and from the result of your test? (d) Among a host of different factors that are claimed to have triggered the economic crisis of 2007-2009,