An investment bank is interested in monitoring the weekly amount (in millions of

dollars) invested in volatile stocks so as to maintain a stable rate of return on a selected

fund. Table 7-31 shows 25 consecutive weeks of the amount invested ($M) in the

fund. Construct appropriate control charts and comment on the stability of invest-

ment. Revise the chart, if necessary, assuming special causes for out-of-control

points. What is your estimate of the standard deviation of the weekly amount

invested?