To evaluate how sensitive beta estimates are to the period over which returns are measured, you now want to repeat the analysis in the last problem using weekly data over the past year.
a. For each firm, as well as for the S&P 500 index, download weekly price information for the past year using the menu options available in the Prices tab for each company.
b. For each firm, calculate the set of weekly returns that correspond to these daily price series.
c. Using weekly returns for the past year, calculate the beta for Walgreens and Exxon Mobil compared to the S&P 500 index.
d. How do your beta estimates for Walgreens and Exxon Mobil differ when using daily versus weekly data in the estimation process? Does your conclusion change about which stock is the riskiest?