Tech Stocks These data give the monthly returns on stocks in three technology companies: Dell, IBM, and Microsoft. For each month from January $1990$ through the end of $2005(192$ months$),$ the data give the return earned by owning a share of stock in each company. The return is the percentage change in the price, divided by $100.$

$($a$)$ Describe and contrast histograms of the three companies. Be sure to use a common scale for the data axes of the histograms to make the comparison easier and more reliable.

$($b$)$ Find the mean, SD$,$ and coefficient of variation for each set of returns. Are means and SDs useful summaries of variables such as these?

$($c$)$ What does comparison of the coefficients of variation tell you about these three stocks?

$($d$)$ Investors prefer stocks that grow steadily. In that case, what values are ideal for the mean and SD of the returns? For the coefficient of variation?

$($e$)$ It is common to find that stocks that have a high average return also tend to be more volatile, with