Nasdaq Weekly chart and the 200dma

Oops wrong title for the above chart

the real chart I wanted to post showing the 200 is the crude and its the 200 week mov av.

Please remind me what DMA is?

I am familiar with:
SMA - Simple Moving Average
EMA/XMA - Exponential Moving Average
WMA - Weighted Moving Average.

DMA=daily moving average run as a simple calculation.

So SMA and DMA are the same animal then? Both just simple averages off the closing price?

yep i like using the notation D for day W for weekly M for Monthly etc

Is that so that you can run a WMA and DMA on the same chart? - for example a daily bar chart has MA's from different time frames such as weeks and months?

yes

I've noticed that the 200 DMA is one of the most popular for long term support and resistance lines on daily charts. Do you know of any research that has been done to support this number (i.e. 200) as the "best" or most reliable over any other value such as 250 or 180 or 220?

I believe the 200 DMA is what the institutions watch closely and trade off of.

myptofvu is quite correct. in fact it goes deeper than that. Bill Gross AKA Pimco have a fiduciary responsibility to react to the 200. once below they must shorten duration and return to benchmarks. The Stock Mutual fund industry has always perceived the 200 as a good long term area to accumulate. sometimes rather than search for an explanation and then try to back test it is easier to just accept and right now we are almost 10 bucks off the low in crude. Now that is a pretty powerful bounce which ought i would assume lead most to be a buyer on dips. but I doubt that they will persue that strategy becasue so many are momogogo traders. Have they not realised that trends areonly a portion of the type of trade and they ignore all the other possible startegies. T. Boone Pickins when crude was 53 said that 50 would not be seen but if it was then 48 was good support. he also said 70 was topside from any bounce.
so there you have it one of the worlds greats in energy told you in advance his strategy.