Do stock prices of competing companies move together? Below are daily closing prices of two computer services firms (IBM = International Business Machines Corporation, HPQ = Hewlett-Packard Company.
(a) Calculate the sample correlation coefficient (e.g., using Excel or MegaStat).
(b) At α = .01 can you conclude that the true correlation coefficient is not equal to zero?
(c) Make a scatter plot of the data. What does it say?

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Daily Closing Price (5) of Two Stocks in March and April 2011 (n 43 days) Date IBM HPQ 159.26 159.45 162.75 42.83 43.16 43.12 4/27/11 4/28/11 4/29/11 169.61 170.02 169.82 41.04 40.53 40.37