Final answer:
The geometric mean return on small/value stocks during the specified period cannot be determined with the given information. Additional data on the specific returns of small/value stocks is needed to calculate the geometric mean return.
Step-by-step explanation:
The geometric mean return on small/value stocks during the 1927-2018 period can be calculated using the total annual rate of return of the S&P 500 index stocks. Unfortunately, the given information does not include the specific return on small/value stocks, but only mentions the overall return on stocks as a group. However, you can calculate the geometric mean return on a set of investment returns by multiplying the individual returns and taking the n-th root, where n is the number of returns. To calculate the geometric mean return, you would need a set of annual returns specifically for small/value stocks.