How can we increase the power of a test without increasing the sample size? According to…

How can we increase the power of a test without increasing the sample size?  According to BusinessWeek, the Standard & Poor’s 500 Index posted an average gain of 13% for 2006.12 If a random sample of 50 stocks from this index reveals an average gain of 11% and standard deviation of 6%, can you reject the magazine’s claim in a two-tailed test? What is your p-value?