Stock screeners are automated tools used by investment companies to help clients select a portfolio of stocks to invest in. The table below lists the...

Stock screeners are automated tools used by investment companies to help clients select a portfolio of stocks to invest in. The table below lists the annualized percentage return on investment (as compared to the Standard & Poor's 500 Index) for 15 randomly selected stock screeners provided by the American Association of Individual Investors (AAII).

9.0          −.1          −1.6       14.6       16.0       7.7          19.9       9.8          3.2          24.8       17.6       10.7       9.1

12.7        -2.3

a.       Find a 99% confidence interval for the average annualized percentage return on investment of all stock screeners provided by AAII. Interpret the result.

b.       A negative annualized return reflects a stock portfolio that performed worse than the S&P 500. On average, do the AAII stock screeners perform worse or better than the S&P 500? Explain.