"your comment yesterday re apple.

i read what you have to say about reversion to the mean. (200 ema) but apple provided they continue their 48 percent yearly increase in profits are on a prospective p/e of 11.9.hardly demanding.

re the 200 ema daily 390 and weekly 269. these seem a long way away. i am advised that the i phone 4s is selling like crazy in china.
at 390 apple would form a large part of my portfolio."

David Fuller's view There is no doubt that Apple (historic, weekly-10yr, weekly-5yr & daily) is one of the great all-time technology stocks. However, all shares become overextended from time to time - in both directions - and the extremes are mainly due to mob psychology rather than fundamentals.

As you point out, the exponential 200-day moving average, which we regard as an approximation of the medium-term trend mean, is currently around $390 and rising fast. Most overextensions relative to the MA, which you can see best on the two weekly charts shown above, have been followed by ranging corrections to the MA. The current overextension is somewhat more dangerous because it is probably the biggest on record for Apple, increasing the possibility of a temporary break of the MA.

For the record, when you click on the 200 MA in the Fullermoney Library, it will always produce a 200-day MA whether you are looking at a daily, weekly or monthly chart. You can change the number of days but the MAs will still be calculated on a daily basis. You also refer to a 200-week MA above, which we would not regard as a useful trend mean, so we do not use it.