Step 1 :Given the price-earnings ratios for eight stocks in a portfolio are 6.2, 9.1, 18.1, 33.6, 12.2, 8.5, 9.1, and 16.4.
Step 2 :To find the mode, we need to identify the number that appears most frequently in the data set.
Step 3 :From the given data, we can see that the number 9.1 appears twice, while all other numbers appear only once.
Step 4 :Therefore, the mode of the data set is 9.1.