When you change the instrument on a chart, you may have noticed that the studies that were on that chart are no longer visible when the chart has a new instrument. Studies are part of an analysis. Each instrument may have one or more analyses that represent an opinion on its future direction. These analyses are analogous to different documents (such as a Microsoft Word document) and are completely independent from each other.
If you would prefer the studies to stick to a chart when you change the instrument, you can lock them so that they will stay on the chart when the instrument is changed. To do this, choose View > Lock Studies from the top menu bar.