The biggest movers traded on the NYSE so far are:

Company | Market Cap | Percentage Change |

Coventry Health Care (NYSE:CVH) | $4.68 billion | +18.5% |

QIHOO 360 (NYSE:QIHU) | $2.14 billion | +8.4% |

Centene (NYSE:CNC) | $2.16 billion | -6.6% |

Las Vegas Sands (NYSE:LVS) | $34.09 billion | +4% |

Aetna (NYSE:AET) | $12.71 billion | +3.5% |

Terra Nitrogen Company (NYSE:TNH) | $4.29 billion | -3.4% |

Boston Beer Co (NYSE:SAM) | $1.41 billion | -3.3% |

**Broker Summary: TD Ameritrade Thinkorswim**

**Coventry Health Care**(NYSE:CVH) has soared 18.5% to reach a current price of $41.42 per share. So far today, the company's volume is 22.5 million shares, 18.8 times its current three-month average. A stock's volume conveys how excited investors are about it. A wide array of ratios can be used by investors to estimate the attractiveness of a potential or existing investment and get an idea of its valuation. The debt-equity (D/E) ratio is a leverage ratio. The debt-equity ratio of 35% is relatively low. This shows that the company's assets are financed primarily through equity. The D/E ratio is not a pure measurement of a company's debt because it includes operational liabilities in total liabilities.

**QIHOO 360**(NYSE:QIHU) is currently trading at $20.10 per share, a 8.4% increase. The company's volume for the day so far is 1.7 million shares. High volume indicates a lot of investor interest while low volume indicates the opposite. Investment valuation ratios provide investors with an estimation, albeit a simplistic one, of the value of a stock. The price/book value ratio is especially important for value investors as it can provide an indication of the true value of a company's assets at a time when its business model may be failing. QIHU's P/B ratio of 6.04 shows that its share price is higher than its book value. This may be a sign that the company is overvalued. To put things in perspective, should be made among companies in the same industry rather than across industries. SEE: Using The Price-To-Book Ratio To Evaluate Companies

At $39.04,

**Centene**(NYSE:CNC) has slipped 6.6%. So far today, the company's volume is 1.7 million shares, 3.1 times the average daily volume. As a stock moves up or down, it is important to pay attention to the trading volume. This indicates the level of interest: the higher the volume, the more the interest. When estimating the value of a particular investment, valuation ratios provide a good basis for assessing the value of an individual stock. The price/sales ratio measures a company's stock market value by its total revenues or alternatively, a company's price per share by its revenue per share. CNC has a low P/S ratio of 0.23. Low P/S ratios are more attractive than high ratios because this indicates that an investor is paying less for each dollar of sales. It is important to keep in mind when looking at the P/S ratio that just because a company is generating revenues, this does not mean that the company is profitable, and in the long run, profits drive stock prices.

**Las Vegas Sands**(NYSE:LVS) is currently trading at $43.08 per share. The company's volume for the day so far is 7.1 million shares. If a stock price makes a big move up or down, volume lets us know the significance of that move. Investors can use valuation ratios as tools to estimate what kind of deal a particular investment is. The price/earnings to growth (PEG) ratio divides a company's P/E ratio by its growth rate of earnings-per-share. LVS' PEG ratio of 1.74 is in line with the industry average. Because of the adjustment for earnings growth rate, the PEG ratio is somewhat more useful than many formulas for comparing companies in different industries.

**Aetna**(NYSE:AET) has moved up 3.5% and is currently trading at $39.39 per share. With 8.6 million shares changing hands so far today, the company's volume is three times the average volume over the last three months. If a stock price moves on high volume, this means that the change is a significant one. Understanding investment valuation ratios allows an investor to assess the true value of an individual stock. The capitalization ratio measures the debt component of the capital structure, or capitalization of a company (i.e., the sum of long-term debt liabilities and shareholder equity) to support operations and growth. AET has a capitalization ratio of 54%, which is on the high end. The company may have trouble meeting operating and debt liabilities on time and surviving adverse economic conditions. A low level of debt and a healthy proportion of equity in a company's capital structure is an indication of financial fitness.

**Terra Nitrogen Company**(NYSE:TNH) has fallen 3.4% and is currently trading at $223.95 per share. The company is currently trading a volume of 17,991 shares. When a stock price moves up or down, watching the volume is a good way of identifying how significant that shift is. Valuation ratios like the price to earnings (P/E) ratio, the price to earnings growth (PEG) ratio, the price to sales (P/S) ratio, the price to book (P/B) ratio, and the dividend yield are useful in determining how attractive a potential or existing investment is. There are generally two price/earnings ratios calculated: the first, called the trailing Price/Earnings ratio, is calculated using the previous years actual earnings; the second, called forward Price/Earnings ratio, is calculated using the next year's estimated earnings. P/E ratio for TNH is 14.5. A high P/E ratio indicates a stock that is expensive, while a low P/E ratio indicates a stock that is cheap. SEE: How To Find P/E And PEG Ratios

After a decline of 3.3%,

**Boston Beer Co**(NYSE:SAM) has hit a share price of $105.57. So far today, the company's volume is 31,091 shares, 0.4 times the average daily volume. If a stock price makes a big move up or down, volume lets us know the significance of that move. It is important for an investor to estimate the value of any potential or existing investment; valuation ratios make this easier. The price/book value ratio is calculated by dividing the current stock price by the company's book value per share. SAM's stock is trading for more than its book value with a P/B ratio of 6.48. This implies that investors expect management to create more value from a given set of assets and/or that the market value of the firm's assets is significantly higher than their accounting value. A weakness of the P/B value ratio is that while the price component is easily determined by looking at the stock quote, the book value component is more difficult to estimate and more open to individual interpretation and analysis. SEE: How Buybacks Warps The Price-To-Book Ratio

**The Bottom Line**No matter the economic climate, Wall Street will always have stocks that make major moves each week. It is important to weigh current activity against historical performance when making any investment decisions. Keep in mind that all these ratios should be compared against historical numbers and industry information in order to get a more complete picture.