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Volatility is defined as the price range for a period, divided by the average price for the period: So, to derive the Daily Volatility on 7/1/2009 of 2.5%, the price range for the day (4.13) was divided by the average price (164.79). Daily Volatility (the daily range as a portion of the daily average price) is plotted in green. Blue is Weekly Volatility, which is the weekly range as a portion of the weekly average price. This is a different concept from the weekly average of daily volatility. For reference, the price is plotted in red. The remaining marks on the plot correspond to the Volatility measured across several time intervals. Investors often make a distinction between the concept of Volatility, and the concept of Risk. Academics define them to be exactly equivalent, but as can be seen here, there is good reason to distinguish between the levels of volatility or risk experienced across different time frames. During 9 years, the Average Quarterly Volatility of ISRG stock price has been 47% while the Average Daily Volatility has been 5%. |
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If you have ever seen a "yield curve" you should be able to understand the concept behind this "yield curve". These Volatility Curves each apply to a discrete time interval. As the timespan across which Volatility is measured increases, the Volatility is expected to increase. However, as seen in this plot of the ISRG Volatility Curve, the increase is not constant. |
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A frequency distribution of the green points on the first chart (the daily volatility) yields this histogram. |
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In a similar vein, the Frequency Distribution of the Quarterly Volatility is plotted here. This is the distribution of the values plotted in purple on the top chart from this page. |
Refined Volatility Risk Analysis for ISRG : |
| Wednesday, July 01, 2009: We have news on Pitney Bowes Inc., ticker symbol PBI. A significant moving average event has happened. Also, there are breaking events concerning Public Service Enterprise Group Inc. and Pinnacle West Capital Corporation. From the News Archive: (7/1/2009 ) A favorable event happened at The Travelers Companies, Inc.. Meanwhile, bad news came from Fiserv, Inc., MeadWestvaco Corp., and Nicor Inc.. |