大多數移動平均線使用給定資產收盤時的價格用以計算。但是需要註意的是不是總是這樣。移動平均線的計算可能選用開盤、收盤、高點、低點甚至是總價價格。盡管這些計算的區別很小，但是還是可能影響到你的分析。
找到合適的時間週期
因為大多數移動平均線代表所有計算日期的平均值，值得註意的是時間週期不總是使用天。移動平均線的計算可以使用分鐘、小時、週、月、季度甚至是年。為什麼一個當日交易員關心50天移動平均線對未來幾週造成什麼樣的影響呢？在另一方面，當日交易員會註意50分鐘移動平均線以用來和過去幾個小時比較相對成本。一些交易員甚至過去三分鐘的平均價格來判斷短期動量。
移動平均線不是萬無一失的
正如你所了解的，金融市場中沒有任何事情是確定不變的，當然使用技術指標時也一樣。如果股票每次都能在主要移動平均線反彈那麼我們都能賺很多。使用移動平均線的一個主要缺點是當一個資產趨強烈時它的作用會不太明顯。
對價格行為的反映
使用移動平均線的交易員將會快承認試圖讓一個移動平均線對趨勢變化產生反映而不太敏感的讓交易員過早的進入或者退出一個倉位將成為一個難題。短期移動平均線在大規模變化發生之前確定趨勢變化會很有用，但是不利的是這這種技巧可能在進出倉位是造成雙重損失，因為移動平均線對價格變化反映十分快快速。因為交易信號的質量將很大程度上取決於計算用的時間週期，所以我們非常建議使用其他技術指標確定移動平均線進行的預測。
警惕滞後性
因為移動平均線是滞後指標，交易信號總是發生在價格充分移動之後。這種滞後性對交易員十分不利可能導致他們在最不合適的時間進入倉位。例如，短期移動平均線交叉移動到長期移動平均線之上的唯一情況是最近價格在上升，許多交易員把這當成牛市信號。在這當中出現的最主要問題時在交叉之前價格很可能已經有大幅上漲。
Moving Averages: Factors To Consider
By Casey Murphy, Senior Analyst ChartAdvisor.com
Data Used in Calculation
Most moving averages take the closing prices of a given asset and factor them into the calculation. We thought it would be important to note that this does not always need to be the case. It is possible to calculate a moving average by using the open, close, high, low or even the median. Even though there is little difference between these calculations when plotted on a chart, the slight difference could still impact your analysis.
Finding an Appropriate Time Periods
Because most MAs represent the average of all the applicable daily prices, it should be noted that the time frame does not always need to be in days. Moving averages can also be calculated using minutes, hours, weeks, months, quarters, years etc. Why would a day trader care about how a 50-day moving average will affect the price over the upcoming weeks? On the other hand, a day trader would want to pay attention to a 50-minute average to get an idea of the relative cost of the security compared to the past hour. Some traders may even use the average price over the past three minutes to gauge an uptake in short-term momentum.
No Average is Foolproof
As you know, nothing in the financial markets is for certain - certainly not when it comes to using technical indicators. If a stock bounced off the support of a major average every time it came close, we would all be rich. One of the major disadvantages of using moving averages is that they are relatively useless when an asset is trending sideways, compared to the times when a strong trend is present. As you can see in Figure 1, the price of an asset can pass through a moving average many times when the trend is moving sideways, making it difficult to decide how to trade. This chart is a good example of how the support and resistance characteristics of moving averages are not always present.
Responsiveness to Price Action
Traders who use moving averages in their trading will quickly admit that there is a battle between trying to make a moving average responsive to changes in trend while not allowing it to be so sensitive that it causes a trader to prematurely enter or exit a position. Short-term moving averages can be useful in identifying changing trends before a large move occurs, but the downside is that this technique can also lead to being whipsawed in and out of a position because these averages respond very quickly to changing prices. Because the quality of the transaction signals can vary drastically depending on the time periods used in the calculation, it is highly recommended to look at other technical indicators for confirmation of any move predicted by a moving average. (For more on various indicators, see Introduction To Technical Analysis.)
Be ware of lagging
Because moving averages are a lagging indicator, transaction signals will always occur after the price has moved enough in one direction to cause the moving average to respond. This lagging characteristic can often work against a trader and cause him or her to enter into a position at the least opportune time. For example, the only way for a short-term moving average to cross above a long-term moving average is for the price to have recently moved higher - many traders will use this bullish crossover as a buy signal. One major problem that often arises is that the price may have already experienced a large increase before the transaction signal is presented.As you can see in Figure 2, the large price gap creates a buy signal in late August, but this signal is too late because the price has already moved up by more than 25% over the past 12 days and is becoming exhausted. In this case, the lagging aspect of a moving average would work against the trader and likely result in a losing trade. Check out the next section of this tutorial to learn about trading strategies involving moving averages.
本文翻譯由兄弟財經提供
文章來源：http://www.investopedia.com/university/movingaverage/movingaverages3.asp