This column was originally published on RealMoney on Oct. 5 at 11:03 a.m. EDT. It's being republished as a bonus for readers.

Today, I'm going to look at the chart of SanDisk ( SNDK), without those darned distracting secondary indicators. But before doing that, let's briefly consider exactly what it is that these nasty indicators do ... and don't do. These are very, very simplistic explanations, but they'll work for now.

First, Wilder's Relative Strength Index (RSI) is a simple measure of momentum. Within a specific period of time, RSI compares the gains of a stock against the losses of that stock. When the average gains within the period under study (say, 14 days) outweigh the average losses, RSI moves higher. If this imbalance continues, the RSI moves higher still -- the upside momentum is stronger. That's pretty much it for RSI. Would I base a trading decision on RSI? Nope. But I like having some empirical data on momentum. It's also really easy to use when I search for stocks with particular momentum characteristics.

Money flow is a measure of buying and selling pressure within a specific period of time. This pressure is calculated by putting in a volume component. Assuming that the close is dominated by the professionals (while the open is dominated by the amateurs), then the location of the closing price relative to the day's range can be informative. Are the pros buying or selling? High-volume days receive a greater weighting than low-volume days because more volume means more pressure; light volume means minimal interest in the stock. In the final analysis, does the degree of money flow impact my P&L? Nope, but it gives me some kind of idea what the pros are doing relative to what they were doing the last time the underlying stock was moving in the same direction. It's a small piece of data but it's free, so I'll take it.

The Accumulation-Distribution, or A-D, Line that I use (there are a few different versions) is a lot like money flow, only easier to understand. Rather than using only that price and volume data within a defined period of time (say, the last 20 days), the A-D line just sums the data, packing new data onto existing data. As such, it's slower to react to quick changes. That's all I have to say about the A-D line because Barry Ritholtz has covered this indicator better than I ever could.

I don't use any of these indicators to predict price movement. Price movement is pretty random, notwithstanding the weekly charts of Encana ( ECA), Valero ( VLO) or Exxon Mobil ( XOM), but people tend to be predictable. When their investments or trades go bad (or good), folks can usually be counted on to react the same way: call it the " wisdom of crowds ."

When I look at charts I see crowds. Price movement will always elicit an emotional response from those who have a financial commitment to the stock. It is this emotional response that I try to game. When the crowd has a similar financial commitment (e.g., everybody bought at around $40), then the crowd can be counted on to react the same way when the price drops from $41 to $39. Many will sell, driving the price even lower. It's an "If..., then...." proposition. I can't predict price movement right now -- only liars can do that. That's why all those silly "Pick the Real Chart from the Random Charts" contests are just silly.

Now, let's look at the crowd around SanDisk ( SNDK). As a substitute for roll call, I'll just analyze the crowd with a simple price/volume daily chart.

    1. The crowd was pretty benign from March through July. There were just random price movements because of an absence of a catalyst to get the crowd emotionally involved. The long horizontal "price-by-volume" bars in the mid-$20's indicate the large number of trades at that wide level. There is lots of financial/emotional commitment.

    2. Big earnings and very aggressive buyers. In fact, the price-by-volume bars show that no trades occurred around $30 due to the aggressive buying of the crowd. Those who are waiting for the stock to drop to more favorable prices continue to be disappointed with each passing day ... as the price moves higher still. One-by-one, these reluctant buyers capitulate, paying up for the stock and pushing prices ever higher.

    3. The crowd is now milling around. Look at the increased length of the price-by-volume bar at the $45 level. Some folks are prudently taking profits, thus creating enough supply that new buyers won't have to pay $50 in late September -- they bought stock for $45. This "churning" at the end of September is important. It effectively gives the crowd a higher basis in the stock, reducing the crowd's tendency to take profits. The longer a stock churns at the same level, the greater the number of folks who have the same basis in the stock -- thus making it a bit easier to apply an "If..., then...." analysis. By the way, that's why I am attracted to low volatility conditions. When you know what cards the majority of the crowd is holding, you have a good chance of capitalizing on their reaction to price movement. But I digress.

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