Table 9.6.2 shows the performance of stocks recommended by securities firms.
a. Compute the average and briefly describe its meaning.
b. Compute the standard deviation and briefly describe its meaning.
c. Compute the standard error of the average and briefly describe its meaning.
d. Find the two-sided 95% confidence interval for the mean performance of stocks recommended by similar brokerage firms during this time period, viewing the data set as a random sample from this idealized population.
e. Find the two-sided 90% confidence interval and compare it to the 95% confidence interval.
f. Find the one-sided 99% confidence interval statement to the effect that the mean performance was at least as good as some number.
g. Suppose you decide that, had the data come out with an average performance loss, you would have used a one-sided confidence interval statement that the mean performance was no larger than some number (in place of your answer to part f ). In this case, and using the same data table, is your answer to part f a valid confidence interval statement? Why or why not? If not, what should you do instead?
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TABLE 9.6.2 Performance of Stocks Recommended by Securities Firms, One-Year Rate of Retum Firm A.G. Edwards Bear Stearns Credit Suisse F. B Edward Jones First Union Sec. Goldman Sachs J.P. Morgan Sec. Lehman Bros. Merrill Lynch Morgan Stanley D.W PaineWebber Prudential Securities Raymond James Salomon S.B U.S. Bancorp Piper Performance -0.3% -14.3 -4.2 -5.3 -38.3 9.6 16.2 -22.0 12.3 1.0 -29.1 -22.5 43.9 -15.7 -5.4