Extracted from http://forum.channelnewsasia.com/viewtopic.php?p=4403888&sid=94cdbd73aba2ff73674827c62db2afc6 written by Dust
When US economic data is good, dollar & Dow gain, else dollar & Dow drops.
When Dollar Index drops due to USD devaluation (QE, inflation etc), Oil goes up, previous metal, commo & stocks goes up.
When Dollar Index drops due to economic woes, Oil will NOT go up. This is because demand is expected to go slow.
When Dollar Index drops, Oil, commo, Euro, Dow all go up. Until Oil goes up too high, Dow will start to drop, so it drop together with Dollar Index. This is because a high oil is bad for companies, bad for stocks.
For precious metal, Gold & Silver will not react the same. When Dollar Index drops due to economic woes, Gold may go up as it is viewed as alternative safe haven, but not Silver. In a troubled economy, Silver will fail as an industrial metal.